SQL Server 2019 drive block size formatting vSAN

Gary Paquette 0 Reputation points
2023-02-05T18:38:27.07+00:00

Hi - on the MSFT web site for performance tuning it mentions that one should format the drive at 64K block size.

VMware has an article saying the you should NOT use anything but 4K if on a vSAN, so which one is it?

It is expensive to make these changes in a large business dependent on SQL Server.

We tried 64K and latency was high, tried 4K and latency got much better.

It is difficult for us to decide what is correct as you are the vendor?

HELP!

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  1. CosmogHong-MSFT 22,541 Reputation points Microsoft Vendor
    2023-02-06T09:15:27.0033333+00:00

    Hi @Gary Paquette

    Not familiar with vSAN, but since it is suggested to use 4K on vSAN and you did have a test that 4K works better, then just format the driver at 4K.

    Best regards,

    Cosmog Hong

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  2. Olaf Helper 40,576 Reputation points
    2023-02-06T09:25:49.24+00:00

    SQL Server stores data in pages = 8 KB and reads extents = 8 pages = 64 kb; that's which a sector size of 64 kb is suggested.

    See Pages and extents architecture guide

    VMware has an article saying the you should NOT use anything but 4K if on a vSAN,

    They may mean for the system drive, but not for a data drive.

  3. Erland Sommarskog 100.8K Reputation points MVP
    2023-02-09T22:12:25.4166667+00:00

    Here is the link I am referring to: https://kb.vmware.com/s/article/83134

    I don't read that document as recommending a 4K block size. They recommend a 4K-aligned block size. So 64K is good, and they give that as an example.