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We have several VMware ESXi hosts accessing multiple datastore stored on a fiber channel SAN.

We have found that some of the hosts are still set to "Most recently used" mode for their multipathing policy.

I would like to change these remaining hosts to use "Round Robin", as I understand that woud be the best option in our scenario, but I would like to know if changing this policy while in a live environment, has any effect on connectivity to the datastores?

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Generally not no but it would be useful to know exactly what make and model your array is as not all support the active/active ALUA model that RR best serves.

  • Thanks for this. The hosts use QLogic 8Gb QLE2560 HBAs, connecting via SANBox 5800v switches, to a dual controller HP P2000 G8 fiber channel SAN. I think everything will support it, as a couple of our hosts are already set to this. – James Edmonds Jun 2 '17 at 11:50
  • Ah I know P2000's (presumably you mean a G3) - they're active/active so you can definitely use RR and move to RR with only a momentary (subsecond) latency blip if any. :) – Chopper3 Jun 2 '17 at 12:51
  • Yep, meant G3, not G8 ;) – James Edmonds Jun 2 '17 at 14:23
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No, there's usually no impact.

This setting can be changed on the fly, assuming the correct "plumbing" is in place.

  • Thank you for your answer. Yes I think all plumbed in correctly, as two hosts are already using this particular policy. I will go ahead and pull the trigger. – James Edmonds Jun 2 '17 at 11:51
  • Note I will accept Choppers answer, only because it was a couple of minutes before yours, and he had the suggestion of also providing my HBA/Array details. If I could mark both as correct I would. – James Edmonds Jun 2 '17 at 11:53
  • @JamesEdmonds Whatever. – ewwhite Jun 2 '17 at 12:19

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