Set Microsoft SQL Servers To Use 4KB Block Size When residing on vSAN
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Set Microsoft SQL Servers To Use 4KB Block Size When residing on vSAN

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Article ID: 326854

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Updated On:

Products

VMware vSAN

Issue/Introduction

As described in KB 83134 vSAN Performance may be degraded when not using 4KB aligned I/O's. This document is written to assist in ensuring that MS SQL is using 4KB aligned I/O. As this relates to a non-VMware product, please consult with your SQL vendor with any questions or concerns on this information.

Symptoms:
  • MS SQL Server is displaying lower performance than expected when using vSAN, and I/O from MS SQL to the datastore is not 4KB aligned.
  • vSAN IOInsight reports show misaligned I/O traffic. 


Environment

VMware vSAN 6.x
VMware vSAN 8.0.x
VMware vSAN 7.0.x

Cause

As described in KB 83134 vSAN Performance may be degraded when not using 4KB aligned I/O's.

Resolution

  • Microsoft KB kb3009974 describes the issue and solution as seen from the SQL server side by setting a trace flag. 
  • As of vCenter/ESXi version 7.0 and higher IOInsight is included in vCenter. You can use IOInsight to check if VMs are using 4KB aligned I/O for best vSAN performance.


Additional Information

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