vSphere and PowerPath/VE - Maximum LUNs to a host and maximum paths to a LUN

[VirtualProUK]

I am currently implementing a new 5 host vSphere cluster, each host has 2 HBA cards and PowerPath/VE installed. This is currently giving us 4 paths down to the storage array, i.e. 2 down to the switch and then it fans out from there to the multiple ports on the Storage Processors.

A third party IT supplier provided us with a report on vSphere best practices based on their experience in the field. Within that report they recommended that we present no more than 15 datastores to a host at any one time. The problem I have is that my plan is to repsent 30 LUNs as datastores to the cluster, so I'm trying to work out where they could be getting this from and have being doing a bit of digging and this is what I found.

The current vSphere configuration maximums is obviously 256 LUNs per HBA and there is an upper limit of 32 paths to a LUN.

So with 2 HBA's I can have 128 LUNs per ESX Host? Now if I add powerpath/VE and I have 4 paths to that LUN does that reduce me to a maximum of 64 LUNs per host? Further still when I get my array upgraded this weekend with 2 additional Front end FC ports per storage processor and that makes 8 potential paths to the LUN would that cut me down to 32 Luns per host as a maximum?

The 8 paths causes another potential issue in that I will then have 8 Paths per Host giving me a total of 40 paths to a LUN which exceeds the maximum number of paths to a LUN. I'd probably look to utilise the zoning to balance the use of all 8 front end FC Ports, only allowing an an ESX host to see 4 paths at any one time.

Appreciate if anyone can assist in verifying any of my thoughts on this subject.

Regards

VirtualProUK

[VirtualProUK]

Sort of answered my own question on this one

The 32 paths per LUN is a per host per lun limit as opposed to a paths per LUN limit as I thought. The number of ESX hosts accessing a LUN does not come into the calculations, this is what I was doing wrong

So in the scenario where I have 4 paths to the storage as I do with PowerPath/VE I can still have 256 LUNs per host. This is because the maximum LUN paths per host is 1024, (4 paths x 256 Luns)

If I do increase the number of paths to 8 per lun then I would be limited to 128 LUNs. 8 paths x 128 LUNs = 1024 LUN Paths.