We are in the process of migrating some of the vmfs volume from one HP EVA (1) to a newer EVA (2). In preparation of the new volume (LUN) on the new EVA, I was wondering about the following. I know if the volume are from the same EVA, we can't use the SAME LUN ID and present it to the same host. But if we have volume from 2 SAN EVA, can the new volume LUN ID from EVA2 be the same as the old volume LUN ID from EVA1? Or would this be a big no no
Yes. ESX will see the LUNs as coming from two different EVAs. Think of the overall address: vmhba0:0:0:1, vmhba0:1:0:1, etc. My example numbers may not be realistic, but basically the 2nd or 3rd digit in the address represents the EVA you are connected too. Think of a fully qualified domain name: serverA (LUN ID) may get you where you want to be. But what about the multitudes of serverA out there? Throw in the domain name and you now have a very specific serverA. Same for LUNs. ESX sees the LUN as part of an device (EVA1, EVA2, etc). So the entire address of the LUN is taken into account.
Right, this works.
It is the second digit (the target address) which maps to an EVA controller port.
However, if there is any chance that want to introduce Continuous Access (CA) in the future, I would plan ahead and make LUN addresses unique.Otherwise, you could end up with collisions after a failover and have to resignature some VMFSes (had to do it once, fortunately only for one VMFS).