So, there's definitely a lot of discussion around using NFS in virtualization scenarios. Although about 1.5 years old, this blog post is still very relevant.
http://viroptics.pancamo.com/2007/11/why-vmware-over-netapp-nfs.html
Given some recent discussion with a moderator (not sure if I should name names?), I just wanted to highlight that post given I've found it pretty useful -- useful enough I wrote up my own summary to have handy whenever I get into NFS discussions with customers -- here's my summary as well (full credit goes to the post above but thought I'd put it here as well in case helpful for anyone).
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Ranking these in order of importance....
- Deduplication - possible to use deduplicated space savings with LUNs but MUCH more complicated (have to mess with fractional reserve, LUN thin provisioning, etc. -- possible to get caught overprovisioning and have real issues)
- VMware Datastore sizing -- easy datastore growth (possible with VMFS) and shrinking (not possible with VMFS)
- Larger datastores - no need to keep datastores smaller like with VMFS - up to 16 TB
- Snapshots - can retrieve individual vmdk's from snapshots and/or mount vmdk's from snapshots for single file restore
- SMVI - main benefit is ability to do faster VM restores (uses SnapRestore rather than LUN clone so can instantly restore a single VM to any previous snapshot)
- VMDK Thin Provisioning
- Ease of addition - somewhat easier than LUNs/VMFS
- VMFS/RDMs - no need to deal with them
- Single-file FlexClone (future feature) - can clone a vmdk instantly for fast provisioning
- No single disk I/O queue as with iSCSI/FC so performance limitations are purely governed by pipe size and disk array size.
- Faster failover to SnapMirror remote copies (less steps plus faster steps) - no need to do LUN resignaturing
- ESX server I/O is small block and extremely random meaning that bandwidth is less important (i.e. GigE works well).
- Can dump individual VM's via NDMP
- No FC zoning, switch cost, HBA's, compatibility matrices, or LUN IDs
