What is Data?

Data is a collection of raw facts from which conclusions can be drawn.

Letters, photographs, movies, word documents, etc. are all examples of data.

What are the two catagories of data?

Structured and Unstructured

Describe Structured Data

Structured data is organized in rows and columns in a rigidly defined format so that applications can retrieve and process it efficiently. 

Describe Unstructured Data

Data is unstructured if its elements cannot be stored in rows and columns, and is therefore difficult to query and retrieve by business applications. 

Examples of unstructured data are images, PDFs, documents, audio / video, email attachments, x-rays, etc. 

Define Information

Information is the intelligence and knowledge derived from data. 

Examples of intelligence could be the buying habits of customers and the health histories of patients.

What is the value of information to a business?

1. Identifying new business opportunities.
2. Identifying patterns that lead to changes in existing business.
3. Creating a competitive advantage. 

How is the type of storage to be used determined? 

The type of storage used is based on the type of data and the rate at which it is created and used. 

Describe RAID

Redundant Array of Independent Disks.  RAID is used in all storage architectures such as DAS, SAN and so on. 

Discribe DAS

Direct Attached Storage.  Connects directly to the server (host) or a group of servers in a cluster.  Storage can either be internal or external to the server.  External DAS alleviated the challenges of limited internal storage capacity. 

Describe SAN

Storage Area Network.  This is a dedicated, high performance Fibre Channel (FC) network to facilitate Block Level communication between servers and storage.  Storage is partitioned and assigned to a server for accessing its data. 

What are the benefits of SAN?

SAN offers scalability, availability, performance and cost benefits compared to DAS. 

Describe NAS

Network Attached Storage.  Dedicated storage for File Serving applications.  Connects to an existing communication network (LAN) and provided file access to heterogeneous clients. 

What are the benefits of NAS?

NAS offers higher availability, scalability, performance and cost benefits compared to general purpose file servers. 

What is IP SAN?

Internet Protocol Storage Area Network.  One of the latest evolutions in storage architecture.  IP SAN is a convergence of technologies used in SAN and NAS.  It provides Block Level communication across a LAN or WAN resulting in greater consolidation and availability of data. 

What are the five core elements of Data Center Infrastructure? 

1. Application / User Interface
2. Database (More commonly referred to as a Database Management System)
3. Server and Operating System
4. Network
5. Storage Array

What are the seven key requirements for data center elements? 

1. Performance
2. Availability
3. Scalability
4. Security
5. Data Integrity
6. Capacity
7. Manageability

What are the four activities within the Information Life Cycle Management Process?

1. Classifying data
2. Implementing Policies
3. Managing the Environment
4. Organizing Storage Resources

**Classifying Data is the most difficult activity in the process**

What are the benefits of implementing Information Life Cycle Management?

1. Improved Utilization
2. Simplified Management
3. Simplified Backup and Recovery
4. Maintaining Compliance
5. Lower Cost of Total Ownership

What are the three most basic components of a storage system environment? 

1. Host
2. Connectivity (Network)
3. Storage Array

What are the physical components of a host? 

1. CPU
2. Storage
3. Input / Output (I/O) Device

What are the three methods of communication between I/O devices and the host?

1. User to Host (Keyboard, Mouse, etc.)
2. Host to Host (via Network Interface Card)
3. Host to Storage Device (via Host Bus Adapter)

What are the logical components of a host?

1. Applications
2. Operating System
3. File System
4. Volume Manager
5. Device Drivers

**Note: Host Bus Adaptors interface on the back end**

What are the logical components of a host?

• Application
• Operating System

What are the two application data access classifications?

1. Block Level (Data stored and retrieved in Blocks specifying the LBA)
2. File Level (Data stored and retrieved by specifying the name and path of the files)

Define Protocol

A defined Format for communication between sending and receiving devices. 

What are the three major communication protocols for system components? 

1. Tightly Connected Entities
2. Directly Attached Entities
3. Network Connected Entities

Give three storage media options

1. Magnetic Tape
2. Optical Disks
3. Disk Drives

What are the key components of a disk drive?

1. Platter
2. Spindle
3. Read / Write Head
4. Actuator Arm Assembly
5. Controller

**All of these items are housed in the Head Disk Assembly**

What are the two ways of accessing data on a platter?

1. Cylender, Head, Sector (CHS)
2. Logical Block Addressing (LBA)

What are the things that affect disk drive performance? 

1. Electromechanical Device
2. Disk Service Type

What are the components that comprise service time?

1. Seek Time
2. Rotational Latency
3. Data Transfer Rate

What are the three seek time specifications? 

1. Full Stroke
2. Average
3. Track to Track

Define 'Little's Law'

• It is the relationship between the number of requests in a queue and the response time. 
• N=a x R
  • N = Total number of requests in the system
  • a = The arrival rate
  • R = Average response time

What does RAID provide?

• Increased Capacity
• Higher Availability
• Increased Performance

What are the components of a RAID Array?

• Host
• RAID Controller
• RAID Array
  • Physical Array
  • Logical Array
  • Hard Disks

What are the common RAID Levels?

• 0
• 1
• Nested RAID
• 3
• 4
• 5
• 6

Describe RAID 0

Describe RAID 1

Disk Mirroring

Describe Nested RAID

• Combines the benefits of multiple RAID configurations.
  • 0+1: Striping & Mirroring.  Commonly Called a Mirrored Stripe.  The process of striping across HDDs is performed then the entire stripe is mirrored.
  • 1+0:  Mirroring & Striping.  Refferred to as a Striped Mirror.  The incoming data is first mirrored and then both copies of data are striped across multiple HDDs. 

Describe RAID Parity

• Parity is a method of protecting striped data from HDD failure without the cost of mirroring.
• An additional HDD is added to the strip width to hold parity.
• Parity is a mathematical construct that allows re-creation of the missing data.
• It is a redundancy check that ensures full protection of data without maintaining a full set of duplicate data. 

Describe RAID 3

• Stripes data for high performance and uses parity for improved fault tolerance. 
• Parity information is stored on a dedicated disk drive so that data can be re-constructed it a drive fails. 
• ALWAYS reads and writes complete stripes of data across all disks.
• Provides good bandwidth for the transfer of large volumes of data. 
• Used in applications that involve large amounts of sequential data such as video streaming.

Describe RAID 4

• Stripes data for high performance.
• Uses parity for improved fault tolerance.
• Unlike RAID 3, disks in RAID 4 can be accessed independently so that specific data elements can be read or written on a single disk without read or write of the entire stripe.

Describe RAID 5

• Drive (strips) are independently accessible
• Parity is distributed across all disks
• Preferred for messaging, data mining, medium performance media serving and Relational Database Management System (RDBMS) implementations in which Database administrators (DBAs) optimize data access.   

Describe RAID 6

• Dual Parity
• Distributes parity across all disks
• Can survive two disk failures
• Rebuild operation may take longer due to the presence of two parity sets. 

What is a 'Hot Spare'?

Referrs to a spare HDD in a RAID array that temporarily replaces a failed HDD of a RAID set.

What is EMC^2's Best practice concerning Hot Spares?

For every two Disk Array Enclosures (DAE) one Hot Spare will be used.

What is an intelligent Storage System?

RAID Arrays that are:

• Highly optimized for I/O processing
• Hove large amounts of cache for improving I/O performance
• Have operating environments that provide:
  • Intelligence for managing cache
  • Array resource allocation
  • Connectivity for heterogeneous hosts
  • Advanced array based local and remote replication options

What are the benefits of an intelligent storage system?

• Increased capacity
• improved performance
• easier data management
• improved data availability & protection
• Enhanced business continuity & support
• Improved security and access control

What are the components of an intelligent storage system?

1. Front end
2. Cache
3. Back end
4. Physical disks

What is the function of the 'Front End' in an intelligent storage system?

The front end provides the interface between the storage system and the host.  It consists of two components:

1. Front End Ports
2. Front End Controllers

What is the function of a front end port?

The front end ports enable hosts to connect to the intelligent storage system. 

Each front end port has processing logic that executes the appropriate transport protocol, such as SCSI, FC or iSCSI for storage connections.

What is the function of a front end controller?

The front end controllers route data to and from cache via the internal data bus. 

When cache receives write data, the controller sends and acknowledgement message back to the host.

Controllers optimize I/O processing by using command queuing algorithms. 

Describe command queuing

Command queuing is a technique implemented on front end controllers.  It determines the execution order of received commands and can reduce unnecessary drive head movements and improve disk head movements and improve disk performance. 

What are the most commonly used command queuing algorithms? 

1. First in First Out (FIFO):  Default algorithm where commands are executed in the order in which they are received. 
2. Seek Time Optimization: Commands executed based on optimizing read /write head movements which may result in reordering of commands.
3. Access Time Optimization:  Commands are executed based on the combination of seek time optimization and an analysis of rotational latency for optimal performance.

Describe Cache

Describe the ways that cache is implemented in write operations

• Write Through:  Data is placed into the cache and immediately written to disk, and an acknowledgement is sent to the host.

• Write Back:  Data is placed in the cache and an acknowledgement is sent to the host immediately. 

What is a Read Cache Hit?

If the requested data is found in the cache it is called a read cache hit or a read hit and the data is sent to the host without any disk operation. 

What is a Cache Miss?

If the requested data is not found in the cache, it is called a cache miss and the data must be read from disk. 

Describe two cache management algorithms implemented by intelligent storage systems to proactively maintain a free set of pages.

• Least Recently Used (LRU):  An algorithm that continuously monitors data access in cache and identifies the cache pages that have not been accessed for a long time. 

• Most Recently Used (MRU):  An algorithm that is the converse of LRU.  In MRU the pages that have been accessed most recently are freed up or marked for reuse. 

Describe 'Watermarking' in cache management

Flushing is the process of commuting data from the cache to the disk.  On the basis of the I/O access rate and pattern, high and low levels called Watermarks are set in cache to manage the flushing process.  This process provides headroom in the write cache for improved performance.  There are three watermarks:

1. 100%
2. High Water Mark
3. Low Water mark

Describe 'Idle Flushing'

Idle Flushing occurs continuously, at a modest rate, when the cache utilization level is between the high and low watermark. 

Describe 'High Watermark Flushing'

Activated when cache utilization hits the high watermark.  The system dedicates some additional resources to flushing.  This type of flushing has minimal impact on host I/O processing. 

Describe 'Forced Flushing'

Forced Flushing occurs in the event of a large I/O burst when the cache reaches 100% of its capacity, which significantly affects the I/O response time.  In Forced Flushing, dirty pages are forcibly flushed to disk. 

Describe two methods of Cache Data Protection

The risk of losing data held in the cache can be mitigated by:

• Cache mirroring:  Each write to cache is held in two different memory locations on two independent memory cards.
• Cache vaulting:  A set of physical disks called vault drives are used to dump the contents of the the cache in the event of a power failure. 

In an intelligent storage system, what is the 'back end'?

The back end provides the interface between the cache and physical disks.  From the cache data is sent to the back end and then routed to the destination disk.  the back end consists of two components:

• Back End Ports: 
• Back End Controllers:  Communicates with the disks when performing reads and writes and also provides additional, but limited temporary data storage. 

What is a LUN?

Physical drives or groups of RAID Protected drives can be logically split into volumes known as Logical Unit Numbers (LUN).  The use of LUNs improves disk utilization by only allocating the portion of disk space needed by the host thereby leaving the remainder of disk space to be allocated to other hosts. 

What is LUN Masking?

• LUN Masking is an access control mechanism that provides data access control by defining which LUNs a host can access. 
• LUN masking is typically implimented at the front end controller. 
• LUN Masking ensures that volume access by servers is controlled appropriately, preventing unauthorized or accidental use in a distributed environment. 
• Usually implimented on staorage arrays.

Describe the capabilities of a high end storage array

**Also referred to as Active - Active Arrays**

• Large storage capacity
• Huge cache to service host I/Os
• Fault tolerance architecture
• Multiple front end ports and support to interface protocols
• high scalability
• ability to handle large amounts of concurrent I/Os
• Designed for large enterprises

**Symmetrix is an example of a high end storage system**

Describe the capabilities of a Midrange storage array

**Also referred to as Active - Passive Arrays**

• Host can perform I/Os to LUNs only through active paths
• Other paths remain passive until active path fails
• Have two controllers, each with cache, RAID controllers and disk drive interfaces
• Designed for small and medium enterprises
• less scalable than a high end array

**CLARiiON is an example**

Describe the characteristics of the CLARiiON CX-4

• Support for Ultraflex technology
• Scalable up to 960 disks
• Supports flash drives
• Supports RAID 0,1, 1+0, 3, 5, 6
• Supports up to 16GB of cache per controller (2 controllers = 32GB total)
• Supports storage based local and remote data replication via SnapView (Local) and MirrorView(Remote)
• CLARiiON Messaging Interface (CMI)
• Stanby power supply
• FLARE Storage Operating Environment

Describe the characteristics of the Symmetrix DMX-4

• Incrementally scalable to 2,400 disks
• Dynamic global cache memory (16GB - 512GB)
• Advanced processing power
• High data processing  bandwidth (up to 128 GB/s)
• Supports RAID 1, 1+0 (AKA 10 for mainframe), 5, 6
• Storage based local and remote replication through TimeFinder (Local) and SRDF (Remote)
• Utilizes Direct Matrix Architecture
• Each memory director connects to each front end director
• Uses the Enginuity OS

Describe the characteristics of the Symmetrix VMAX Series

• 96 to 2,400 drives up to 2 PB (3x more usable capacity)
• One to eight VMAX engines
• Upt to 1TB global memory
• Twice the host ports (FC, iSCSI, Gb Ethernet, FICON) up to 128 ports
• 8Gb/s FC, FICON and FC SRDF
• Twice the back end connections for flash
• Quad core 2.3GHz processors to provide more than twice the IOPS

What is DAS?

Direct Attached Storage is an architecture where storage connects directly to servers. 

• Uses Block Level protocol for access
• Internal HDD and tape libraries are examples of DAS

***Can be internal or external***

Describe Internal DAS

Internal DAS is internally connected to the host by a serial or parallel bus.

• The physical bus has distance limitations and can only be sustained over short distances for high speed connectivity. 
• Most internal buses can only support a limited number of devices

Describe External DAS

In External DAS Architectures, the server connects directly to the external storage device.  In most cases, communication between the host and the storage device takes place over SCSI or FC protocol. 

• External DAS overcomes distance and device count limitations of Internal DAS 

What are the benefits of DAS?

• Ideal for data provisioning
• Quick deployment for small environments
• Simple to deploy
• Reliable
• Low capital expense
• low complexity

What are the four DAS connectivity options?

1. ATA and SATA
2. SCSI
3. FC
4. Buss and Tag (primarily for external mainframe)

What are the two types of DAS Management?

1. Internal:  Host provides disk partitioning and file system layout.
2. External:  Array based management, lower TCO for managing data and storage infrastructure.

What are some of the challenges of DAS?

• Scalability is limited
  • Number of connectivity ports to hosts
  • number of addressable disks
  • distance limitations
• Downtime is required for maintenance with internal DAS
• Limited ability to share resources
  • Array front end port, storage space
  • resulting in islands of over and underutilized storage pools

What is the definition of SCSI?

Small Computer System Initiative

• SCSI is all about an initiator sending a command to a target.

What does SCSI communication involve? 

• SCSI Initiator Device:  Issues commands to SCSI target devices.
• SCSI Target Device:  Executes commands issued by initiators. 

SCSI -1: Defined cable length, signaling characters, commands, and transfer modes, Uses 8-bit narrow bus (supoports 8 devices)

SCSI -2: Defined common Set (CCS), 16 bit, improved performance and reliability

SCSI -3: Latest version, comprised different but related standards, rather than one large document.

*Can support between 8 and 16 devices

What is SCSI Addressing?

Used to uniquely number (0-15) identify hosts and devices. the UNIX naming convention is used to identify a disk and the three identifiers - initiator ID, target ID, and a LUN.

Structure and Organization of FC Data

Exchange Operation (conversation): enables two N_ports to identify and manage a set of information units.

Sequence (Sentence): refers to a contiguous set of frames that are sent from one port to another.

Frame (word): the fundamental unit of data transfer at Layer 2.  *Each frame can contain up to 2,112 bytes of payload

What SCSI ID has the highest priority?

7

What is a SCSI Port?

• SCSI ports are physical connectors that the SCSI cable plugs into for communication with a SCSI device.
• SCSI device may contain initiator port, target port and target / initiator port.
• To cater to service requests from multiple devices, a SCSI device may also have multiple ports.

WWN

World Wide Names: a unique 64-bit identifier which is static to the port.  Used to physically identify ports.

Like a NIC's MAC Address

Every HBA has one

Burned into an array port

What is SAN?

Storage Area Network.  Is a dedicated high speed network for block level access. 

• Carries data between servers (AKA Hosts) and storage devices through FC switches. 
• Provides Block Level data access.
• Consolidates resources centralizing storage and management
• Scalability (theoretical limit 15 million nodes)
• Secure access

Fibre Channel Addressing

is dynamically assigned during fabric login. Used to communicate between nodes within SAN. Like an IP Address on a NIC

Address format: 24 bit, dynamically assigned

What are the components of SAN?

A SAN consists of three basic components:

1. Servers
2. Network infrastructure
3. Storage

These components can be further broken down into the following key elements:

1. Node Ports
2. Cabling
3. Interconnecting Devices (such as FC switches or hubs)
4. Storage Arrays
5. SAN Management Software

Fibre Channel Protocol Stack (5)

FC-4: Upper Layer protocol

FC-2: Transport Layer

FC-1: transmission layer

FC-0: physical interface

FC-3 has not been implemented

Fiber Channel Architecture Overview

• used channel technology
• high performance with low protocol overheads
• FCP is SCSI-3 over FC network
• Has five layers

What is Fibre Channel SAN and its components?

moves blocks of data over fibre optic cables using SCSI commands between initiator and target.

Components: director/switch, host (node), storage (node), cables, management software to control ports/switches.

FLOGI

Fabric Log In: between N-Port to F_port

Between node and switch (switch/array or initiator/target)

1st in process

What are the two types of optical cables?

1. Single Mode:  Can carry single beams of light with a distance of up to 10 KM.
2. Multi Mode:Can carry multiple beams of light simultaneously at a distance of up to 500M.

(Note: multi mode cable can suffer from modal dispersion)

PLOGI

Port Login : between N_Port to N_Port (initiator to target initial contact)

2nd in process

PRLI

Process login (figure out how to talk by a common language - SCSI)

3rd in series

What are the different types of SAN connectors?  

Node Connectors:

• Standard Connector (SC) Duplex Connectors
• Lucent Connector (LC) Duplex Connector

Patch Panel Connectors

• Straight Tip (ST) Simplex Connectors

ISL

Inter Switch Links - connects two or more FC Switches to each other using E-Ports.

Used to transfer host to storage data as well as the fabric management traffic from one switch to another

Also one of the scaling mechanisms in SAN connectivity

What are the different port types on SAN?

N_Port (node port): end point in the fabric to the switch.

NL_Port (node loop port): supports arbitrated loop topology. Goes into a HUB.

E_Port (expansion port): FC port that forms the connection between two FC Switches.

F_Port (fabric port): a port on a switch that connects an

FL_Port (public loop): a fabric port that participates in FC-AL. Connected to the NL_Ports on an FC-AL loop.

G_Port (generic port): can operate as an E_Port or an F_Port and determines its functionality automatically during initialization.

What are the three commonly used SAN Interconnecting Devices?

• Hubs:  Physically connect nodes in a logical loop or a physical star topology.
• Switches:  More intelligent than hubs and directly route data from one physical port to another.   
• Directors:  Departmental switch.

Describe the SAN Interconnectivity Option called FC-SW?

Fibre Channel switched fabric (FC-SW) - provides interconnected devices, dedicated bandwidth, and scalability.

Also know as fabric connect.

Describe the SAN Interconnectivity Option called FC-AL?

Fibre Channel Arbitrated Loop (FC-AL):  devices are attached to a shared loop. Devices on the loop must arbitrate to gain control of the loop. At any given time, only ONE device can perform I/O operations on the loop.

What is the simpliest form of SAN Interconnectivity?

Point to Point - two devices are connected directly to each other (like DAS).

Describe SAN Management Software? 

• A suite of tools used in a SAN to manage the interface between host and storage arrays.
• Provides integrated management of SAN environment.
• Web based GUI or CLI

What is Core-Edge Fabric?

&

What are the two types?

two types of switch tiers - the edge tier (comprised of switches) and the core tier (enterprise directors)

Single Core: all hosts are connected to the edge tier and the core tier.

Dual Core: can be expanded to include more core switches - enables load balancing.

Describe the Fabric Topology Mesh and name the different types

each switch is connected directly to the other switches by using ISLs. Promotes enhanced SAN connectivity.

Full Mesh: every switch is connected to another switch in the topology - appropriate for a smaller # of switches (4).

Partial Mesh: several hops or ISLs may be required for traffic to reach its destination. Can cause latency issues.

Describe the term Zoning in Fabric Management

is an FC switch funtion that enables nodes within the fabric to be logically segmented into groups that can communicated with each other.

Access control done on the switch or fabric vs. LUN masking which is done on the array

Setting up a relationship between initiator and target.

What are the Storage Over IP protocol Options?

• iSCSI: 
  • Is SCSI over IP. 
    • Has IP encapsulation
    • Hardware-based gateway to Fibre Channel Storage
  • Used to connect servers
• FCIP: 
  • Fibre Channel-to-IP bridge / tunnel
    • Point to point
    • Fibre Channel end points

**Used in DR Implementations**

What is iSCSI?

• An IP base protocol that establishes and manages connections between storage, hosts and bridge devices over IP. 
• Carries block level data over IP based networks, including Ethernet networks and the Internet. 
• Is built on the iSCSI protocol by encapsulating SCSI commands and data in order to allow these encapsulated commands and data blocks to be transported using TCP/IP packets

Describe the components of a Zone

Members: nodes within the SAN that can be included in a zone

Zones: comprise a set of members

Zone Set: comprise of a group of zones that can be activated or deactivated as a single entity fabric

*Only one zone set per fabric can be active at a time

Describe the Types of Zoning

sets up the relationship to set what initiator can see what target

Port Zoning (hard zoning): uses FC addressing of the physical ports to define the zones (most secure - EMC general Practice).

WWN zoning (soft zoning): uses world wide names to define zones.  

.

What are the components of iSCSI?

• iSCSI host initiators:
  • Host computer using a NIC or iSCSI HBA to connect to storage
  • iSCSI initiator software may need tobe installed
• iSCSI Targets: 
  • Storage array with embedded iSCSI capable network port
  • FC-iSCSI bridge
• LAN for IP Storage Network:
  • Interconnected Ethernet switches and / or routers

What is NAS and what are the benefits?

Network attached storage. It is an IP based file-sharing device attached to a local area network.

• Efficiency
• Flexibility
• Centralized storage
• Simplifies management
• Scalable
• High Availability
• Secure

What are the iSCSI host connectivity options

• Software Initiators: 
  • Code that can be loaded onto a host to provide the translation between the storage I/O calls and the network interface
• TCP Offload Engine (TOE):
  • Moves the TCP processing load off the host CPU onto the NIC Card to free up processing cycles for application execution. 
• iSCSI HBA:
  • A network interface adapter with and integrated SCSI ASIC (Application Specific Integrated Circuit)
  • Simplest option for boot from SAN 

What are the component of NAS?

• NAS Head (CPU and Memory)
• NIC Card(s)
• Operating System to manage NAS functions
• NFS (unix) and CIFS (microsoft)
• Industry-standard storage protocols
• Storage Array

Describe the NAS File Sharing Protocols

CIFS - Common Internet File System Protocol

• Microsoft Environment based on the server message block protocol

NFS - Network File System Protocol

• UNIX environment file sharing protocol

Describe the NAS I/O Process

1. requester packages the I/O request into TC/IP to a remote file system which is handled by the NAS
2. The NAS converts the I/O into an appropriate physical storage request (block level I/O)
3. When the data is returned from the physical storage pool, the NAS processes and repackages it into a file protocol response.
4. The NAS packages this response into TCP/IP again and forwards it to the client through the network.

What are the three iSCSI Topologies?

• Native Connectivity: Do not have and FC components; perform all communication over IP.
• Bridged Connectivity: Enable the co-existance of FC with IP by providing iSCSI to FC bridging functionality.
• Combining FCP and Native Connectivity

Describe the types of NAS Implementations

Integrated NAS: - has all components of NAS in a single enclosure. Connects to the IP network to provides connectivity to the clients and service the file I/O requests.

Gateway NAS: has independent NAS head and one or more storage arrays (2 protocols)

What are the two ways in which iSCSI discovery takes place?

• Send Targets Discovery: 
  • Initiator is mutually configured with the target
• Internet Storage Name Service (iSNS): 
  • Initiators and targets automatically register themselves with iSNS server
  • iSNS is a client / server model

Describe how Managing an Integrated System (NAS Connectivity) works

Both the NAS component and the storage array are managed via NAS management software

Describe managing a Gateway System (NAS)

NAS component managed via NAS Management software and the storage array is managed via array management software

What are the two types of iSCSI names?

• IQN: iSCSI Qualified Name
  • IQN (ex: iqn.2008-02.com.example:optional)
• EUI: Extended Unique Identifier
  • (ex: eui.020234k2034j03D34)

EMC Celerra

Celerra is a dedicated high-performance infrastructure for FILE LEVEL I/Os

Celerra NS40G (gateway NAS) - Celerra NS-960 (Integrated NAS)

Consists of:

Data movers (file servers in cabinet)

Control Station (sets up data movers and initially configs them)

Specialized OS - DART - Linux Red Hat

Describe how to join the building blocks in Integrated NAS and Gateway NAS?

Integrated: the system is assigned to dedicated NAS storage. No other SAN hosts connected to the storage - whole array is dedicated solely to NAS provisioning.

Gateway: the NAS system is assigned separately apportioned storage within the array. Two separate sections for SAN and NAS.

What is an FCIP Frame? 

• Encapsulates FC frames in IP packets
  • FCIP router is used for encapsulation
  • FC Router at other end removes IP wrapper and sends FC data to other fabric
• Includes security, data integrity, congestion and performance specifications

What is Fibre Channel over Ethernet? 

• A new protocol that maps Fibre Channel protocol naively over Ethernet.
• Based on two new standards that are currently in active development:
  • FCoE standard, being developed by T11 Fibre Channel Interfaces Technical Committee
  • Enhanced Ethernet standard, being developed by the Ethernet IEEE Data Center Bridging Task Group
• Enables the consolidation of SAN traffic and Ethernet traffic onto a common 10 Gigabit network infrastructure 
• FCoE requires jumbo frames (2180 byte) support to prevent a Fibre Channel frame from being split into two Ethernet frames  

Describe Lossless Ethernet

To support Fibre Channel frames over Ethernet, no frames can be dropped throughout the entire transmission.

• No frame drop due to congestion or buffer overflow.
• PAUSE capability of Ethernet is used to achieve the lossless fabric.

Describe the FCoE Physical Elements

• Host Interface: CNA (converged network adapter) - ex: PCIs card on host consolidates NICs and HBAs

• 10 Gbps connectivity options: either copper or standard optical

Describe the benefits of FCoE

• Lower capital expenditure
• Reduced power and cooling requirements
• Enabler for consolidated network infrastructure
• Lower TOC

What is Virtualization?

The technique of abstracting physical resources into a logical view.

• Increases utilization
• Simplifies resource management
• Reduces downtime (planned and unplanned)
• Improved performance of IT resources

What are the challenges of storing fixed content? 

• Fixed content is growing at more than 90% annually.
  • New regulations require retention and data protection
• Often, long term preservation is required
• Simultaneous multi-user online access is preferable to online storage
• Need faster access to fixed content
• Traditional storage methods are inadequate

What is a swap file (used in memory virtulization)?

is a portion of the hard disk that functions like physical memory (RAM) to the operating system.

Describe Network Virtualization

creates virtual networks whereby each application sees its own logical network independent of the physical networks.

EX: Virtual LAN (VLAN) - centralized configuration of devices

What are the traditional storage solutions for archive? 

Three categories of archival solutions are:

1. Online
2. Nearline
3. Offline

• Based on the means of access
• Traditional archival solutions were offline

What is Server Virtualization?

enables multiple operating systems and applications to run simultaneously on different virtual machines created on the same physical server (or group of servers).

Provides a layer of abstraction between the OS and the underlying hardware.

Any # of virtualized servers can be established.

What is storage virtulization?

Process of presenting a logical view of physical storage resources to hosts

Logical storage appears and behaves as physical storage directly connected to host

• Examples: Host Based, LUN Creation (thin LUN), Tape
• Benefits
• Increased storage utilization
• Adding or deleting storage without affecting apps
• Non-disruptive data migration

What are the shortcomings of traditional archival solutions? 

• Tape is slow
• Optical is expensive and requires vast amounts of media
• Recovering files from tape and optical is often time consuming
• Data on tape and optical is subject to media degradation
• Both solutions require sophisticated media management

What does SNIA Storage Virtulization Taxonomy provide?

the Storage Networking Industry Association (SNIA) storage virtulization taxonomy provides a systematic classification of storage virtulization, with three levels: WHAT, WHERE, and HOW

Specifies the types of virtulization:

1. block
2. File
3. Disk
4. Tape
5. Any

What is Content Addressed Storage?

• Object oriented, location-independent approach to data storage
• Repository for the "objects"
• Access mechanism to interface with repository
• Globally unique identifiers provide access to objects

What are the benefits of CAS?

• Content authenticity
• Content integrity
• Location independance
• Single instance storage
• Retention enforcement
• Record level protection and disposition
• Technology independence
• Fast record retrieval

Describe block level storage virtualization

-Ties together multiple independent storage arrays.

• Presented to host as a single storage device
• Mapping used to redirect I/O on this device to underlying physical arrays.
• -Deployed in a SAN environment

*Non-disruptive data mobility and data migration

-Enable significant cost and resource optimization

What are the Physical Elements of CAS?

• Storage devices (CAS based)
  • Storage Node
  • Access node
• Servers (to which storage devices get connected)
• Client

Describe the Application Programming Interface (API)?

• A set of function calls that enables communication between applications or between an application and an operating system.

Describe file-level virtualization

addresses the NAS challenges by eliminating the dependencies between the data accessed at the file level and the location where the files are physically stored.

Before virtualization, each NAS device of file server is physically and logically independent.

Describe EMCs Invista

provides block-level storage virtualization in heterogeneous storage environments.  Supports dynamic volume mobility for volume extension and data migration between different storage tier without any downtime.

What is a BLOB?

• The distinct bit sequence (DBS) of user data represents the actual content of a file and is independent of the file name and physical location.

Describe the difference between CPC and DPC and how they see targets and initiators

Control Path Cluster - storage device running invista and is located OUTSIDE of the data path (handles any requests which are NOT I/Os)

Data Path Controller - special purpose SAN switch/blade which operates inside the data path and handles the I/O requests. If its not an I/O then it routes the request to the CPC.

Describe EMC Centera Architecture

deals with the storage and retrieval of fixed content

Based on RAIN (redundant array of independant node - access and storage)

Linux OS, CentraStar sw to impliment CAS functions

1 TB of usable capacity in each node

two 24-port 2 gigabit internal switches

Is self healing

What is a C-Clip? 

• A package containing the user's data and associated metadata
• C-Clip ID is the CA that the system returns to the client application

What data protection does the Centera Use?

CCP - content protection parity

CPM - Content protection mirrioring

Describe Content Address

• An identifier that uniquely addresses the content of a file and not its location. 
• Unlike location based addresses, content addresses are inherently stable and, once calculated, they never change and always refer to the same content

Describe the C-Clip Descriptor File (CDF)

• The additional XML file that the system creates when making a C-Clip.  This file includes the content addresses for all referenced BLOBs and associated metadata. 

What are the features of CAS?

• Integrity Checking
• Data protection (local and remote)
• Load balancing
• scalability
• Self - diagnosis and repair
• Report generation and event notification
• Fault tolerance
• Audit trails

How does CAS store a data object?

1. End users present the data to be archived to the CAS API via an application
2. The API separates the actual data (BLOB) from the metadata and the CA is calculated from the object's binary representation. 
3. The content address and metadata of the object are then inserted into the C-Clip Descriptor File (CDF)
4. The CAS system recalculates the object's CA as a validation step and stores the object.
5. An acknowledgement is sent to the API after a mirrored copy of the CDF and protected copy of the BLOB have been safely stored in the CAS system
6. Using the C-Clip ID, the application can read the data back from the CAS system. 

How does CAS retrieves a Data Object?

1. The end user or an application requests an object
2. The application queries the local table of C-Clip IDs stored in the local storage and located the C-Clip ID for the requested object
3. Using the API, a retrieval request is sent along with the C-Clip ID to the CAS System
4. The CAS system delivers the requested information to the application, which in turn delivers it to the end user

What is virtualization?

Its a technique of abstracting physical resources in to a logical view.

Benefits: increases utilization, simplifies resource management, reduces downtime, improved performance of IT resources

What are the four forms of virtualization?

How does virtual memory work?

makes an application appear as if it has its own contiguous logical memory independent of the existing physical memory resource.

Done by virtual memory managers (VMM)

Space used by VMMs on the disk is known as a swap file

What is a SWAP file?

the portion of the hard disk that functions like physical memory (RAM) to the operating system.

- gives the illusion physical space on the memory

How does Network Virtualization Work?

createsvirtual networks whereby each application sees its own logical network independent of the physical network.

EX: Virtual LAN (VLAN) - enables centralized configuration of devices located in the physically diverse locations.

What are the benefits of Virtual Memory?

• Removed physical - memory limits
• Run multiple applications at once

What are the benefits of Virtual Networks?

• Common network links with access-control properties of separate links
• Manage logical networks instead of physical networks
• Virtual SANs provide similar benefits for SANs

How does Server Virtualization work?

Enables multiple operating systems and applications to run simultaneously on different virtual machines created on the same physical server (or group of servers).

Provide a layer of abstraction between the OS and the underlying hardware

VMWare

What is Business Continuity  

• Preparing for, responding to and recovering from an application outage that adversely affects business operations.
• Addresses unavailability and degrades application performance
• An integrated and enterprise wide process and set of activities to ensure "information availability"  

What are the benefits of server virtualization?

• break dependencies between operating system and hardware
• Manage OS and application as a single unit
• Strong fault tolerance
• Hardware - independent 

How does storage virtualization work?

the process of presenting a logical view of the physical storage resources to a host.  Appears and behaves as physical storage

Examples:

1. Host-based volume management

2. LUN Creation (thin LUN)

3. Tape virtualization

What are the benefits of storage virtualization?

• Increased storage utilization
• Adding or deleting storage without affecting applications availability
• Non-disruptive data migration - KEY

Describe SNIA Storage Virtualization Taxonomy?

Storage Networking Industry Association: provides a systematic classification of storage virtualization, with three levels - what, where, and how

It specifies the types of virtualization: block, file, disk, tape, or any other devices.

What is Information Availability (IA)?  

• Refers to the ability of an infrastructure of function according to business expectations during its  specified time of operation.
• Can be defined in terms of three parameters:
  • Accessibility:(information should be accessible in the right place and to the right user
  • Reliaability: Information should be reliable and correct
  • Timeliness:  Information must be available whenever required

Describe the Multi-Level Approach to Storage Virtualization

Server: path management, volume management, replication

Storage Network: path redirection, load balancing - ISL trunking, Access control - zoning (ex - powerpath

Storage: volume management - LUNs, access control (LUN Masking), replication, RAID

What are the two types of storage virtualization configs?

Out of Band - the virt. env. confi is stored externally to the data path - minimal latency

In Band - implementation places the virtualization function inside the data path - additional latency

What are some causes of information unavailability?

• Planned Outages (80%)
• Unplanned Outages (20%)
• Disaster (<1%)

What is block-level storage virtualization?

Ties together multiple independent storage arrays and presents them to the host as a single storage device.  Mapping is used to direct the I/O on this device to underlying physical arrays

Deployed in a SAN environment

*Non-disruptive data mobility and data migration

Cost reduction

What are some of the impacts of Downtime?

• Lost productivity
• Damaged Reputation
• Lost Revenue
• Financial Performance
• Other expenses

What is file level virualization?

address the NAS challenges by eliminating the depenpendancies between the data accessed at the file level and the location where the files are physically storage.

EX: RAIN Finity

How is Information Availability Measured? 

• IA=Uptime / (Uptime + Downtime)
  • Uptime = Mean Time Between Failure (MTBF)
  • Downtime = Mean Time to Repair (MTTR)

EMC Invista

Enables NON-DISRUPTIVE data migration. Provides block-level storage virtualization in heterogeneous storage environments.

What are main hardware components of Invista?

Control path cluster (CPC): stores configurations parameters OUTSIDE of the data path.

Data Path Controller (DPD): special purpose SAN switch blade which routes I/Os INSIDE the data path.  If its not an I/O then it sends it to the CPC

What is Disaster Recovery?

• Coordinated process of restoring systems, data and infrastructure required to support ongoing business operations in the event of a disaster
• Restoring previous copies of data and applying logs to that copy to bring it to a known point of consistency
• Generally implies the use of backup technology

What are the benefits of virtual provisioning?

• Reduce administrative costs (people)
• Reduce storage costs by deploying assets as needed
• Reduce operating costs (fewer disks)
• Reduce downtime

What is Disaster Restart? 

• The process of restarting from disaster using mirrored consistent copies of data and applications
• Generally implies the use of replication technologies

In virtual provisioning - what is thin pool expansion?

Adding drives to a thin pool on disruptively increases available shared capacity for all the Thin LUNs in the pool

Describe the "Cloud" Approach to Storage

A cost effective approach to handling internet era data growth.

Five requirements: infinite scale, no boundaries, operationally efficient, self-managing, self-healing

What is Recovery Point Objective?

• A point in time to which systems and data must be recovered after an outage
• The amount of data loss that a business can endure

Define cloud computing

is an emerging IT development, deployment, and delivery model, enabling real time delivery of products, services and solutions over the Internet

Services Include: Saas, PaaS, Iaas

Ex: Google aps, salesforce.com

What are the key attributes of Cloud Services?

Offsite third party provided

Accessed via Internet

Minimal to no IT skills required to implement

Provisioning

Pricing

User interface

system interface

Shared resources

What is Recovery Time Objective?

• The time within which systems, applications or functions must be recovered after an outage.
• The ammount of downtime that a business can endure and survive.

What is EMCs Cloud Infrastructure?

What is Backup?

is an additional copy of data that can be used for restore and recovery purposes. Used when the primary copy is lost or corrupted.

Can be created by:

-Simply copying the data

-Mirroring the data

• Identify the critical business functions
• Collecting data on various business processes within those functions
• Business Impact Analysis (BIA)
  • Risk Analysis
    • Assessing, prioritizing, mitigating and managing risk
• Designing and developing contingency plans and disaster recovery (DR) plan
• Testing, training and maintenance

What do organizations perform backups?

1. Disaster recovery

2. Operational - restore in the event of data loss or corruption during routine process

3. Archival - preserver transactions for business and/or regulatory compliance

What needs to be considered before a Backup/Restore Solution is Implemented?

Recovery Point Objective (RPO)

Recovery Time Objective (RTO)

Media type to be used

Where and when the restore operations occur

When to perform the backup

The granularity of the backup (Full, Incr., Cum)

How long to keep the backup

Do you copy the backup

Data - size and location of it

What are the solutions and supporting technologies that enable business continuity and uninterrupted data availability?

• Single point of failure
• Multi-pathing software
• Backup and replication
  • Backup and recovery
  • Local replication
  • remote replication

What are the three types of backup granularity?

Full Backup - all data once per week

Incremental - copies the data that has changed since the last full - faster but slower to get back data

Cumulative - copies the data that has changed since the last full backup. takes longer - easier/faster to recover data

Define Single Point of Failure

• The failure of a component that can terminate the availability of the entire system or IT service.

What are the differnt types of Backup Methods?

• Cold - offline
• Hot - online
• Open File (either have to retry or have a SW agent)
• Point in Time (PIT) Replica
• Backup file metadata for consistency
• Bare metal recovery

What are some advantages of Multi-pathing Software?

• Configures multiple paths to increase data availability
• Helps to recognize and and utilize alternate I/O paths to data
• Provides load balancing to improve data path utilization

Backup Architecture and Process

• Backup Client - sends backup data to backup server or storage node
• Backup Sever  - manages backup operations and maintains backup catalog
• Storage Node - Responsible for writing data to backup device

What are the steps in the backup operation?

1.Start of scheduled backup

2.Backup server retrieves backup related info from catalog

3(a) backup sever instructs storage node to load backup media in backup device

3b. Backup server instructs backup client to send its metadata to the backup server and data to be backed up to storage nodes

4. Backup clients send data to storage node

5. Storage node send media information to backup server

7. Backup server update catalog and records the status

What is local replication?

• Data from the production devices (LUN) is copied to replica devices within the same array
• The replicas can then be used for restore operations in the event of data corruption or other events

Describe Local Replication

• Data from the production devices is copied to replica devices on a remote array
• In the event of a failure, applications can continue to run from the target device

What are the steps in the restore operation?

1. Backup server scans backup catalog to identify data to be restored and the client that will receive the data

2. Backup server instructs storage node to load backup media in backup device

3. Storage node then reads the data and sends to backup client

4. Storage node sends restore metadata to backup server

5. Backup server updates catalog

Describe Backup / Restore

• Backup to tape has been a predominant method to ensure business continuity
• The frequency of backup is dependant on RPO / RTO requirements

What are Direct Attached Backups?

a backup device is attached directly to the client.  Only the metadata is sent to the backup server through the LAN.

- Frees LAN from backup traffic

What are LAN Based Backups?

all servers are connected to the LAN and all storage devices are directly attached to the storage node. The data to be backed up is transferred from the backup client (source), to the backup device (destination), over the LAN, which may affect network performance.

- can minimize impact by config sep networks

Describe some attributes of EMC PowerPath

• Host based software
• Resides between the application and SCSI Device Driver
• Provides intelligent I/O path management
• Is transparent to the application
• Automatic detection and recovery from host to array path failures

What are SAN based backups?

backup devices and clients attached to the SAN

YES THIS IS THE BOOK DEF!  WTF MATE :)

Mixed Backup (2 Clients)

Describe an application server based backups

the NAS head retrieves the data from storage over the network and transfers it to the backup client running on the application server. The backup client sends this data to a storage node, which in turn write the data to the backup device.

-overloads the network

Descride a severless backup in NAS

the network share is mounted directly on the storage node. Avoids overloading the network during backup. Storage node acting as backup client - reads the data from the NAS head and write it to the backup device without involving the application server.

NAS Backup - NDMP- 2 -way

backup is sent directly from the NAS head to the backup device, while metadata is sent to the backup server.

Network traffic is minimized by isolating data from the NAS head to the locally attached tape library. Only metadata is transported on the network.

-uses special protocol

NAS Backup - NDMP - 3 Way

data is not transferred over the public network.  A seperate private backup network must be established between all NAS heads and the "backup" NAS head to prevent any data transfer on the public network in order to avoid congestion.

- uses two NAS heads

- Private network

- used in a multibuilding env (college campus)

• Traditional backup destination
• Low cost
• Portable
• Sequential/linear access
• Multiple streaming

What are the limitations of backing up to tape?

• Reliability (restore performance)
• Sequential access
• can not be accessed by multiple hosts simultaneously
• Needs a controlled environment
• Wear and tear
• Shipping/handling charges
• Tape management challenges
• Need to encrypt data

What are the benefits of backing up to disk?

• Ease of implementation
• Fast access
• More reliable
• Random access
• Multiple hosts can access
• Enhanced overall backup and recovery

What is the recovery time in minutes?

The time from point of failure to return of service to e-mail users

What is a virtual library and its components?

Its an array with special software - tape emulation engine. emulation SW has a database with a list of virtual tapes, and each virtual tape is assigned a portion of a LUN on the disk.

How does EMCs Networker Work?

enables simultaneous access operations to a volume, for both reads and writes, as opposed to a single operation with tapes by making a copy of the production LUN and do a backup from the copy

- works within existing frameworks

-Accelerates and centralized backup process

The client generates tracking info and sends it to the server to facilitate point-in-time recoveries

What is local replication and its uses?

replicating data within the same array or the same data center.

-alernate source for backup

-Fast recovery

-Decision support

-Testing platform

-Data migration

What do you consider when you're going to replicate data?

Types

-Point-in time (PIT): non-zero RPO (how much data you can loose)

-Continuous: near zero RPO

What makes a replica good? - recoverability

/re-startability and consistency

What is consistency in terms of backup?

is the primary requirement to ensure the usability of replica device.

Can be achieved in various ways:

For File System:

-offline - un-mount file system

-Online - flush hot buffers (space in memory)

For Database:

-Offline- shutdown database

-Online- data in hot backup mode

Describe flushing host buffer

What is the dependent write I/O Principle?

Dependant Write: a write I/O that will not be issued by an application until a prior related write I/O has completed - LOGICAL dependency - NOT a time dependency

-is inherent in all DBMS and is nessecary for protection against local outages

What is the process of holding an I/O in database consistency?

the process of quiescing the database.

Steps:

1. hold I/O to all the devices at the same instant

2.Create the replica

3. Release the I/O

What are the two local replication technologies?

Host based array

-logical volume manager (LVM) based mirroring

-File system Snapshot

Storage Array Based

-Full volume mirroring

-Pointer based full volume replication

-Pointer based virtual replication

What is LVM Based Mirroring?

the LVM is responsible for creating and controlling the host-level logical volume.  Components: physical volumes (disk), volume groups, and logical volumes.

Each logical partition in a logical volume is mapped two physical partitions on two different physical volumes.

What is File System Snapshot?

Is a pointer based replica that requires a friction of the space used by the original file system.

-Uses copy on first write (COFW) principle

-Uses bitmap (to track the blocks that have changed on the production/source FS after creation of snap - initially all zero

-Block Map: used to indicate block address from which data is to be read when the data is accessed from the Snap FS - initially points to production/source FS

-Requires a fraction of the space

What are the limitations of host based replications?

-LVM based replicas add overhead on host CPUs

-If host volumes are already storage array LUNs then the added redundancy provided by LVM mirroring is unnecessary

-Host based replicas can be usually presented back to the same server

-Keeping track of changes is a challenge after the replica has been created

Describe how a storage array based local replication works?

-Replication is performed by the Array Operating Environment

-Replicas are on the same array

Types:

-Full-volume mirroring

-Pointer-based full volume replication - Clone

-Pointer -based virtual replication - snap

A clone

-Provides a full copy of the source data on the target

-Target device is made accessible for business operation as soon as the replication session is started

-Point-in- time is determined by the time of session activation

Two modes: Copy On First Access (COFA) and Full Copy Mode

-Clone will be the same size of larger

Describe detached full volume mirroring

After synchronization is complete, the target can be detached from the source and made available for BC operations.

-PIT is determined by the time of detachment

-After detachment, re-synchronization can be incremental

Copy On First Access - Deferred Mode - not a full clone

Primarily used for testing and development

Data is copied from the source to the target on when:

-A write is issued for the first time after the PIT to a specific address on the source

-A read or write is issued for the first time after the PIT to a specific address on the target.

What is full copy mode?

On session start, the entire contents of the source device is copied to the Targer device in the background.

-most vendors also provide SW to track d changes made to the source or target

What is pointer based virtual replication?

SNAPS

-Targets do not hold actual data, but hold pointers to where the data is located.

-A replication session is setup between source and target device. Target devices are accessible immediately when session is started

-Moves data into a resource LUN Pool (RLP)

How are changes tracked in a database after PIT has been created?