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The second factor is network architecture; the performance of NAS storage is highly dependent on network health and utilization. You should isolate your NAS traffic on dedicated physical NICs that aren't shared with virtual machines. You should also ensure that you use a physically isolated storage network that's dedicated to your hosts and NFS servers, and isn't shared with any other network traffic. Your NICs are your speed limit; 1 Gbps NICs are adequate for most purposes, but to take NFS to the next level and experience the best possible performance, 10 Gbps is the ticket. There are a number of network configuration tweaks you can use to boost performance, as well as technology like jumbo frames.
The final factor in NFS performance is the type of NAS storage device you're connected to. Just like any storage device, you must size your NAS systems to meet the storage I/O demands of your virtual machines. Don't use an old physical server running a Windows NFS server and expect to meet the workload demands of many busy virtual machines. Generally, the more money you put into a NAS product the better performance you'll get. There are many high-end NAS systems available that will meet the demands of most workloads.
NAS has its niche
NAS might not be appropriate for every virtualized server environment -- for certain workloads only a FC SAN will do -- but it's certainly attractive and effective for most use cases. In past years, NAS wasn't a viable
BIO: Eric Siebert is an IT industry veteran with more than 25 years of experience who now focuses on server administration and virtualization. He's the author of VMware VI3 Implementation and Administration (Prentice Hall, 2009) and Maximum vSphere (Prentice Hall, 2010).
This was first published in February 2011