We mostly use NAS for our ~200 VM VMware environment and it works great. Here are some of the advantages I can think of off the top of my head for NAS:
- Dedupe is easy. (i.e. the space dedupe saves is immediately available for use in the volume for the VM admin to use. With SAN, space reclaimed by dedupe is available in the volume but not the lun, so you either have to create another lun to use the free space or thinnly provision your volume to gain the space back at the aggregate level.)
- Growing and shrinking the VM datastore is a very easy and quick online process.
- File level cloning in NFS is a very nice feature that allows you to do file-level clones of your vmdk's, saving lots of space if you have lots of identical VM's.
- Snapshot restores are easy. If you enable snapshots on your NFS Vmware datastores, it makes it easy for the VM admin to reach into the .snapshot snapshot directory and grab a recent VM image should he need to restore the vm for some reason. You can also use the filers single-file snap restore feature to restore the vm's to an earlier snapshot should you need.
- If you use snapmirror or snapvault it makes it easy to restore the VM's from these.
Some disadvantages that I know NAS has over SAN are:
- No multipathing, unless you have switches that support cross-stack etherchanneling. So can have a single point of failure.
- Can be a bit more work to get the same level of performance. Make sure you're using jumbo-frames end-to-end, have flow-control setup correctly end-to-end, have a dedicated lan for your traffic and bond some of your ethernet connections together to get a higher throughput than 1g, unless you'd be using 10g.
Those are the things I can think of anyway.
