Term
| Name 3 places you can view/verify storage configuration. |
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Definition
1. Maps - see host to datastore and VM to datastore.
2. Storage Views tab. Requires vCenter Storage Monitoring plug in which is installed by default with vCenter Server and enabled by default
3. Host's configuration tab in the storage/storage adapters section. You can see a list of datastores in either datastore or device view |
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Term
| When does storage contention occur? |
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Definition
| When the demand of the hosts and VMs exceeds the ability of the storage array and/or hbas. |
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Term
| Which ESXtop metrics can help you find out where a storage bottleneck is occuring? (VM, HBA or array level) |
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Definition
davg – this is the average response time for a command being sent to the device.
kavg – this is the average response time a command is in the vmkernel
gavg – this is the response time as it appears to the VM. Usually davg + kavg.
CMD/s – number of IOps being sent to or received from the device or the VM. |
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Term
| Outline the steps to take to resolve storage contention issues (five points) |
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Definition
* Check CPU usage of the VMs and increase queue depth (advanced setting) if needed
* Storage vMotion the VM or VMs to a new LUN with more spindles or add more disks to the LUN in question
* Increase the VMs memory - this will allow for more OS caching which may reduce I/O activity
*Defragment file systems
* Tur off anti-viris on-demand scans |
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Term
| When does storage over-commitment occur |
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Definition
| When using thin provisioned disk. Since thin storage allows you to provision more space than available, it's possible to over commit or fill up the datastore. |
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Term
| How can you avoid or remediate storage over commitment? |
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Definition
| Be sure to use alarms on the datastore in order to find out when a datastore is nearing capacity. If you do run out of space, you can storage vMotion some VMs off the datastore to free up space. You can add additional space to the LUN and either increase the size of the datastore or add an extent. |
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Term
| Outline troubleshooting steps for iSCSI initiators (in addition to general networking troubleshooting guidelines) |
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Definition
* If using the iSCSI initiator as a boot device, the adapter is enabled automatically. Meaning, if you disable it after you have booted, it will re-enable next boot.
* By default, the software adapter is disabled and needs to be activated
3. Software (and dependent hardware) adapters utilize vmkernel networking. Ensure you have proper settings configured on a vmkernel port to use the adapter properly
4. If you are using more than one uplink and using different vSS's, then both the IPs need to be on different IP Subnets
5. If using multiple uplinks on one vSS, then each vmkernel port group must map to a different uplink |
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