Defrag for Windows 2012 R2 Hyper-V CSV volume

[Dave Baddorf]

   My Nimble customers have Cluster Shared Volumes (CSV) and run Windows 2012 R2 Hyper-V VM's on those CSV's.  My question is should I run Windows Defrag on the VM's?  And should I run Windows Defrag on the CSV volumes?  Running a defrag analyze on a CSV volume can be done (see http://blogs.msdn.com/b/clustering/archive/2014/01/02/10486462.aspx) but I am not seeing the output that I've been accustomed to - I don't see a message about "you should/shouldn't defragment this volume" but rather just see messages about Slab Consolidation.  Apparently Windows defrag works differently when the volume is thinly provisioned.  But I can't seem to find very clear information on the best practices of defragrmenting a CSV volume which is thin provisioned.  Which leads me to my above questions:  Should I run defrag at the VM level?  And should I run it on the CSV volume?

  I appreciate any insight that anyone has to offer...

Thanks!  Dave

[Nick_Dyer · Accepted solution]

Hi Dave,

Wherever possible it's advisable NOT to run any defragmentation tools on a Nimble Storage platform. The CASL architecture has a built in defrag tool as part of it's garbage collection process (called sweeping) and is an always-on process running in the background of the file system; running a host-side defrag tool will merely change the layout of the blocks within the CASL architecture, leading to potentially worse performance overall.

[Dave Baddorf]

Thanks for your response, Nick!  I just have one clarification on your response:  When you said that you shouldn't run a Defrag on a Nimble Storage platform I'm assuming that you mean you shouldn't run Defrag on a Windows Hyper-V Host using the Nimble SAN as a Clustered Shared Volume (CSV).  But does your recommendation also include not running a Defrag within the Windows VM's running on the Hyper-V Host?  In other words, do you recommend not running Defrag on either the host nor the VM's?  Thanks for your help!

Dave

[Dave Baddorf]

Does anyone have any comment on whether it is a good idea to defrag a Windows VM when running the guest on a Hypervisor which is storing the VM's on a Nimble SAN?  I realize that I don't want to run defrag on a Windows Host, but how about within a VM?

[Nick_Dyer]

It is not recommended to run host-side defrag on any operating system, physical or virtual.