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JoseTeixeira
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Contributor
‎05-30-2016 04:06 AM
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Multiple PVSCSI with SQL Server

Hi,

Regarding SQL Server virtualization, been trying to find info if there is a positive performance impact on separating Data devices from Log devices into different Paravirtual SCSI Adapters, similar to what is done here [https://books.google.pt/books?id=jrMTBAAAQBAJ&pg=PA155&lpg=PA155&dq=pvscsi&f=false].

There has been a scenario on a client where an additional PVSCSI was added and log devices were separated to the new PVSCSI, showing considerable performance gains. Yet, the doubt remains if it was due to this separation or simply due to the fact that an additional PVSCSI was now present.

Anyone has any insight on this?

Thanks in advance

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MKguy
Virtuoso
Virtuoso
‎05-30-2016 06:29 AM
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Each controller has it's own IO queue with a certain maximum queue depth. By adding additional controllers, you can prevent the queue from overflowing in cases of really high IO workloads (if you physical storage is not the bottleneck already), so it's generally recommended to split different heavy IO virtual disks to different vSCSI controllers as well.

You may also want to consider increasing the controller queue depth:

VMware KB: Large-scale workloads with intensive I/O patterns might require queue depths significantl...

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JoseTeixeira
Contributor
Contributor
‎05-30-2016 02:33 PM
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Thanks for your attention and reply MKguy‌

I should've expanded the question a little further:

Log disks typically are written in a sequential manner, while data disks follow a more random pattern on their r/w, and it is well known that data and log files should be on separate disks due to this difference.

But what about the controllers? Is there a benefit also on keeping these different patterns in separate PVSCSI controllers?

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