Adding second LUN to MS Cluster CSV


We currently have a Windows 2008 x64 R2 3 node Hyper-V cluster using CSV for highly available VM's.  The LUN size for the CSV is set at 2 TB which is the maximum LUN size I can create on our EVA4400.  We are quickly running out of disk space.  Can I add a second LUN to the CSV and retain high availability for our VM's?  My understanding is that all highly available VM's must reside on the same LUN.  Will any other issues result with adding a second LUN to the cluster storage?  If this isn't possible, what other options do I have to increase disk storage for the CSV?

Thanks in advance.

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You can have multiple LUN's.  You need to add it as cluster storage and then make it available under CSV.

I can't remember the exact process but you can do it - will double check in a minute and come back to you.

Out of interest, why are you using such big LUNS?  I've always gone with the view to have more LUNS and make them smaller as you are spreading the load around more on the EVA and if you have to restore a LUN, it's less data to restore.

PHFrenchAuthor Commented:
Thanks for the response.

We currently have a single disk group configured within our EVA.  This is the recommended configuration per HP.  They claim this reduces spindle contention.  The more disks in a disk group the better. As far as the LUN size, it is my understanding that in order to have highly availalbe VM's they all must reside on the same LUN.   I assume if I had 20 100 GB LUN's configured and using CSV it would be transparent to Hyper-V and Live Migration?  Would the ClusterStorage\Volume1 share on one of the Hyper-V hosts be 2 TB in size?  We are backing up each VM individually to disk, then tape so I don't think a full LUN restore would ever be requried unless we had complete data loss on the SAN.

 Thanks Jeff
When I asked about the size of the LUN, I was referring the size that was presented to the HYPER-V cluster - not how it was configured on the EVA.

The last time I set up a HYPER-V cluster, I presented small volumes to the cluster for each particular VM.  For example, if a VM needed 50gb of disk space, I'd present a 55gb piece of disk to the HYPER-V cluster and use it exclusively for that VM.  It allowed me to live migrate one VM at a time if I wanted.

TBH - I never tried having multiple VM's on one single disk under a HYPER-V cluster so I don't know if it's a better way of doing it and I don't know if you could live migrate one server at a time.

Anyway, that aside - I hope I've answered the original question to your satisfaction. :)
PHFrenchAuthor Commented:
That's the advantage to CSV's.  You don't have to configure a single LUN for each VM.  All VM's reside on the same LUN.  This is referenced in MS documentation.  I still need to verify if multiple LUN's configured for a CSV will show as the same size as a single LUN under the ClusterStorage\Volume1 share.

Thanks for your comments.
If you add another volume (LUN) to CSV, it will be available under ClusterStorage\Volume2. So if you're running out of space on the first volume, I think you will have to migrate VMs from the first to the second volume.

Using one big LUN instead of multiple small LUNs isn't necessary, but it has its advantages: if you're using 10 VMs of 50GB, jakethecatuk would present 10 LUNs of 55GB, or 550 in total.
PHFrench would make one LUN of 500GB + 5GB headroom (or maybe 10GB) would only require 505-510GB storage on the SAN: so if you're using multiple VMs, using less LUNs will save diskspace to to less headroom-overhead.

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