ESX 3.5 / EVA4*00 / VCB

[defuseme2k]

Just a quick question that I believe I already know the answer to, but let me elaborate below.

BTW I'm using ESX 3.5, so no fancy path awareness :<

Every LUN I care to worry about is visible to 10 ESX hosts, and 2 VCB proxies. I'm using FIXED pathing per HPs best practice (which I know is a heated debate, not to be had here). I then manually load balanced the ESX side and set the HP EVA not to failback (we monitor heavily). My VCB proxies are using MPIO and the HP DSM, using SQST (there are 4 active paths to everything).

Should I turn of SQST on the VCB proxies? Should I specify the active path to match my ESX hosts and then set the other paths as standby for redundancy sake only? The reason I ask is because if my understanding of ALUA is correct, regardless of what I have the LUN ownership set to via Command View, if an I/O request is received by the proxy controller, then the LUN ownership changes and can cause 'thrashing'. Maybe we haven't noticed is too much because it is at night that backups occur, but I could see with the ESX hosts being set fixed that it would be possible to have this happen while using VCB.

 

[lopoetve]

the EVA is ALUA (and pseudo-active/active) - meaning it doesn't actually thrash the path over. Any read requests to the standby controller are sent through a mirrorlink port (nothing more than a 1Gb connection between controllers), but it doesn't transfer ownership. It's just slow as snot when it has to do that, since it's non-cached and a bloody ethernet cable.

For speed, definitely set path to the controlling owner.

edit: and on 3.5, Fixed is the right thing to do.

 

[defuseme2k]

OK. Well, I read a post on yellow-bricks (depping is the man) today about ALUA, and he had a link in there (toward the middle), but it was more in reference to EMC arrays. I'm not a storage expert AT ALL, but I was worried I could end up having ownership transfered on I/O request like the EMC array he was speaking of. Doesn't sound like the EVA works the same, which is a good thing (I better say here I'm not the storage admin =), but communication between us isn't easy...).

That still doesn't answer my question entirely, though. Should I turn off SQST on the VCB proxy, I guess not? I know the EVA controllers won't switch ownership, and given the way this sounds it wouldn't end up going down an unoptimized path anyway.