James_McCartin
Contributor
Contributor

Does LUN Order Matter?

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If you attached a LUN to multiple hosts, does it matter if the LUN number is the same for all hosts? By LUN number, I mean the SCSI ID, not the UID.

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a_p_
Leadership
Leadership

I'd recommend you keep things simple and present the LUNs to all hosts with the same LUN-ID. As mentioned earlier, using different IDs may not matter with VMFS datastores, but could cause issues with RDM's (see link in my previous post).

André

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nightnicon
Enthusiast
Enthusiast

No functionally it won't matter although they should all see it as the same LUN number anyway.

mcowger
Immortal
Immortal

There are certain scenarios with RDMs where it DOES still matter....

--Matt VCDX #52 blog.cowger.us
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a_p_
Leadership
Leadership

You'll find an interesting blog post regarding this at http://cormachogan.com/2012/09/26/do-rdms-still-rely-on-lun-id/

André

James_McCartin
Contributor
Contributor

This is the LUN number I am referring to:

Capture.PNG

Will this be the same across all hosts, regardless of the order the LUNs are presented to the hosts on the storage side? Is this number the same as the LUN number on the storage side? I think LUNs can be presented in differented orders to the hosts causing different LUN numbers on the storage side.

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a_p_
Leadership
Leadership

I'd recommend you keep things simple and present the LUNs to all hosts with the same LUN-ID. As mentioned earlier, using different IDs may not matter with VMFS datastores, but could cause issues with RDM's (see link in my previous post).

André

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