How to set Round Robin PSP’s default iops limit to 1 for EMC Symmetrix arrays 0

Quick fix

I’ll be brief with this one.  I recently had to find a way to override the Round Robin path selection policy’s (PSP) default iops setting to comply with an EMC standard in order to get support for an ongoing issue.  In this case, I had to change from the VMware default for this setting, 1000 I/O operations per path, to EMC’s standard of 1 I/O operation per path.  I am working with an EMC VMAX array (Symmetrix).

Instead of modifying this on a per-device basis, I chose to create a new SATP rule that simply overrides the default setting.  I chose this path so that I could continue to use host profiles in conjunction with stateless auto deploy for multiple clusters of ESXi hosts.

The command is quite simple (run this from a shell on your host profile ‘source’ host):

esxcli storage nmp satp rule add -s "VMW_SATP_SYMM" -V "EMC" -M "SYMMETRIX" -P "VMW_PSP_RR" -O "iops=1"

 

After running the above command, extract a new host profile and you’re golden.  Hosts will honor the new default value after a reboot.

Thoughts

The setting here in question is actually a highly debated topic.  I will not be diving into details here, as this post is simply made to be used as a quick reference.  You can read more about the debate and get more information regarding other methods for changing this setting from the links below:

EMC VMAX and DMX Symmetrix Storage Array recommendations for optimal performance on VMware ESXi/ESX (2072070)
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2072070

What’s the point of setting “–IOPS=1? ?
http://www.yellow-bricks.com/2010/03/30/whats-the-point-of-setting-iops1/

Changing SATP Claimrules for specific storage configurations
http://www.gabesvirtualworld.com/changing-satp-claimrules-specific-storage-configurations/

Automating the IOPS setting in the Round Robin PSP
http://cormachogan.com/2013/07/08/automating-the-iops-setting-in-the-round-robin-psp/