My Dell tech support told me to disable vaai on my esxi hosts because I'm running the Dell MEM. Is this really recommended? We're going down this path because of various database servers just running incredibly slow. Physical Win7 machine can process the same set of records in 10 minutes. My virtual Win7 takes just over an hour. Any suggestions would be appreciated.
I doubt that disabling VAAI will help with your performance issue, but if Dell support wants this to troubleshoot further, then I guess you don't have much of a choice.
To disable it you need to set the following advanced parameters to 0:
The procedure is described in detail here: VMware KB: Disabling the VAAI functionality in ESXi/ESX
In theory, VAAI improves the performance on the ESXi hosts but at the cost of CPU and Disks usage on the Storage Controller. If amount of CPU and memory that you are trying to save does not justify the Storage CPU & Disk Usage then there is no point in offloading the provisioning tasks to the Storage. However you would see this very rarely but it depends of on the workload that you have provisioned on the storage.
Before disabling VAAI I would compare the performance on both the ESXi hosts and the Storage. If you reduce around 20% of host resources but this results in 99% spikes on the storage array which disrupts other storage tasks then you may disable VAAI. However probe more as to why VAAI should be disabled.
PS: I work for NetApp but this approach can be used for any Storage Infrastructure.
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