Multipath Policy Settings Questions

[sel57]

Hi All,

How it the multipath setting initially set on the datastores? Does the storage decide? We have been seeing degraded performance from IO latency, and a 3PAR support rep recently suggested changing to Round Robin from the default MRU we were running on the 3PAR luns. I'm not sure how this will help because I didn't think Round Robin was link aggregation, rather just rotating paths for pushing IO down.

Anyway, when I checked my paths from an EMC device we also have, they were already set to Round Robin, so I was wondering if the array sets this, and if so, why 3PAR suggests something different than their array sets by default.

[sajal1 · Accepted solution]

Hello sel57,

By default ESXi checks the storage type and then depending on the storage type it sets the default policy best suitable for that storage type. For details you can check the following:

Chapter 23 : Understanding Multipathing and Failover

http://pubs.vmware.com/vsphere-55/topic/com.vmware.ICbase/PDF/vsphere-esxi-vcenter-server-551-storag...

Also you can check at the HCL link. For each storage vendor, type, Firmware version and ESXi version there is a suggested Path Selection Policy. So depending on the storage vendor, type, Firmware version and esxi version the best path selection policy is selected by default.

VMware Compatibility Guide: Storage/SAN Search

For example, in the above link I searched for EMC and ESXi 5.5 U1.

So in short the default is set and tested one and at time of booting the best suitable policy is selected. If there is any specific reason or suggestion from storage vendor then only you should change the default policy otherwise not.

Hope this answers the question.

[sel57]

Thanks Sajal1. Your response was very helpful. I appreciate it.