Enabled ODX In Hosts With Non-Supporting SAN Can Cause CSV Stability Issues

There is an interesting tip in the KB article KB2813630 for Windows Server 2012 clusters with CSV:

To avoid CSV failovers, you may have to make additional changes to the computer after you install the hotfix. For example, you may be experiencing the issue described in the "Symptoms" section because of the lack of hardware support for Offloaded Data Transfer (ODX). This causes delays when the operating system queries for hardware support during I/O requests.

In this situation, disable ODX by changing the FilterSupportedFeaturesMode value for the storage device that does not support ODX to 1.

In other words:

  • Your CSVs are stored on a SAN
  • Your SAN does not support ODX
  • ODX is enabled by default in Windows Server 2012
  • This can (in other words, might but not definitely) cause stability issues during the period when the server queries the SAN for support
  • Disable ODX in this case

Go here to learn more about deploying ODX.  According to that site you can query for the status of ODX support in your server installation (nothing to do with the SAN – check your vendor for ODX support in your SAN) by running:

Get-ItemProperty hklm:systemcurrentcontrolsetcontrolfilesystem -Name "FilterSupportedFeaturesMode"

If it’s got a value of 0 then ODX is enabled in the server.  Set the value to 1 to disable ODX in the current server:

Set-ItemProperty hklm:systemcurrentcontrolsetcontrolfilesystem -Name "FilterSupportedFeaturesMode" -Value 1

There’s no mention of a reboot of the re-configured host but I’m guessing we should take it for granted.

3 thoughts on “Enabled ODX In Hosts With Non-Supporting SAN Can Cause CSV Stability Issues”

  1. Running Set-ItemProperty hklm:systemcurrentcontrolsetcontrolfilesystem -Name “FilterSupportedFeaturesMode” -Value 1 takes effect immediately on my servers. I can flip that switch back and forth and see ODX disable/enable immediately.

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