NFS is great technology when it comes to VMware - thin provisioning by default, no HBAs to mess with, dynamic storage allocation, etc.... however there is one pitfall that I've just noticed on our test lab.
With HBAs, when you ran out of space in a presented LUN, only VMs that had snapshots attached would crash, because they were writing a redo log, and no space was available for that.
Now, with NFS and thin-provisioned VMs (and even thin-provisioned VMs on VMFS) all the VMs have redo logs essentially, so if you run out of space on a volume, all the VMs in that volume are going to crash (which could be a large number fyi).
Thankfully, dynamic allocation of NFS volumes should prevent this, given sufficient warning on your storage.
Wednesday, November 4, 2009
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