NFS is a much simpler way to provision storage in an ESX environment. One thing I like about it is its ability to look at
a shared volume as a filing system. With iSCSI, you get a LUN and have to play by all the rules imposed with VMFS ( which is a fine filing system!) but yet another set of restrictions and overhead.
With NFS, I am not limited to the usage of the specialty tools provided by VMware for filing system operations. I can use traditional Unix/Linux tools
in a fast manner to migrate the VMDK files where I want them. VMFS is optimized as an out of the box clustered filing system and normal tools
do work with objects in this filing system, but performance is slow if you don't use the optimized set of tools provided by VMware.
Another thing I like about NFS presented storage is that I get really easy and accurate usage reports about what my VMware environments are
taking up. I can see exactly where everything is easily and know how much is required and what my anticipated growth should be. With a VMFS
there is a lot of exercises necessary to determine what space is really available for usage and what's held currently in reserve.
Latency being an issue on an NFS server is exactly what causes very poor performance. One thing I like about a dedicated NFS server is being able
to optimize for latency. Usage of the SSD (read/write zillas) which can be incorporated in certain NFS server models helps reduce latency from a spindle level
to be almost a non-issue.
Seriously, for ease of use being the only reason, NFS makes more sense to use. The administration costs in a large environment go down considerably.
The complexity of LUN management, combined with server spraw in a virtual environment makes things complicated enough as it is.
I remember reading an article about a large bank in the west (name left out on purpose!) who did a complete conversion of their existing iSCSI
provisioned storage in VMware to NFS. Justification for it was purely on cost savings related to management of their environment and simplified
disaster recovery procedures.
I've been using NFS for years and considered it first and early on. It was always my first choice when Fibre Channel was not designed in at the beginning
of a project. I still prefer a SAN if I want to get the absolute best performance possible, but when it comes to Ethernet attached storage, NFS is still my