Monday, March 3, 2008

VMWare over NFS vs FiberChannel (FC)

VMWare over NFS has been quite the buzz over the past few months, especially when it comes to NetApp filers like the 3070c. I personally run VMWare over FC connected into a NetApp 3050c on hi-speed fiber channel drives. What I like about it is it's fast and it works well. It's really not that hard to setup and a denial of service attack on my IP network won't hurt my VM's access to the SAN.

With Fiber channel you have to create LUNs for the VMWare box to access. There are 2 schools of though here... either create 1 big LUN and run all your VM's from it - or - create a new LUN for each VM.

With NFS, things change. Apparently you can take advantage of de-duplication, no single disk I/O, and you can use VMDK thin provisioning. What I'd like to see is a good white paper on NFS vs Fiber Channel including setup instructions and why you would choose one over the other.

2 comments:

  1. If you find a white paper on that topic, I'd like to see it too :-)

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  2. I will say, since i wrote this post i've been running over 20 production VM's on NFS on my NetApps and another 20 on fiberchannel. A Couple things here, NFS runs great and the de-duplication has been very useful. It's also been nice for running systems off and ESX Server that is not within fiber distance to my SAN.

    A couple of cons are:
    1. NFS doesn't transfer as quick on my non-disruptive filer upgrades. It works, the systems stall for a short period during the cluster failover process and the VM's are happy... but it does give the system a short period (maybe 10 - 30 seconds) of downtime. Amazingly, our streaming media VM only stalled on the non-buffered video.
    2. It's easy to over subscribe your NFS Share if your using De-Dup and you provision too many systems too quickly. We filled up a volume with systems and de-dup was saving over 80%... but once the changes came to the individual VM's we filled up the volume and eventually caused VM's to not be able to start. I'd recommend only using up to 60% of the de-dup savings as it will eventually catch up to you.

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