Best practice in defragging Virtual servers. ESXi 4.1, Server 2008 R2.

Can you defrag a virtual servers disks like with a physical server?
If I run a defrag on a virtual server, It only analyses the disc and the defrag finishes instantly.

We have several Equallogic SAN's which host the volumes for each virtual guest server.
VM's are managed via vCentre 4.1

What is the best practice in defragging volumes with this design? is there one?
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I touched on this subject recently at this post:

Basically, you have to determine the need based off your virtual infrastructure setup. If you use Thin disks for VMs, it's most certainly a "no" because defrag'ing will touch all your disk and thus 'inflate' your VMDK to thick. This also affects CBT. If you read this brief article about defrag'ing, I think it'll answer your question and you can best decide if you should do it, but mostly, the answer is 'no':


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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Contact you SAN vendor and ask for their recommendation,
Yes, that is one of the recommendations in the article I posted. But again, if you're using thin disks for your VMs and you want to continue doing so, there's really no point in asking your SAN really can't to a defrag. Also, in reality, the performance gain from a defrag tends to be negligible UNLESS there is a lot of file 'movement' that happens on a particular VM or VMs. Then there 'may' be some performance gain.

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MayogroupAuthor Commented:
All good. Thanks for the posts.
I am not trying to say I need to defrag. I realise this is no longer required for windows servers.
I am just wondering what the standard is for SAN technology. I assume there must be something I can do as ongoing maintenance around volumes and VMDK's etc?

I will contact the vendor.
Yes...for SAN specific questions, you'll need to ask your vendor. I know EMC mostly doesn't require it..pretty sure Dell doesn't but others (NetApp, etc.) may.

Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Make sure your Partitions in your VMDKs are ALIGNED!
Good point @hanccocka. @Mayogroup - if you are using Windows OS's below 2K8/Win7, then I *highly* suggest this free tool:

I have tested it out and it works well. There is a video in the URL (towards the bottom of the post) that helps show how to use it.
This thread talks about disk alignment more, as well: (this is the best blog on alignment I've seen out there IMO)

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