Is Optimize needed inside VMWare VMs?

[TimG]

First, thanks for JKDefrag - it is a great program.

I'm now starting to deploy it inside several VMs on a VMWare Server host, running a RAID 10 array.

(At some point, I will also deploy it at the host level. That is for another day.)

It seems to me that there is no good reason to run the Optimize phase inside these VMs. I have confirmed with HDTune that there is no performance drop from the beginning of the virtual disk to the end, so it seems that there is no good reason to run with Optimize enabled. So I have been running it with the "-a 2" option.

Is my reasoning sound, or is there something I am missing?

[isgdre]

In Virtural PC 2007 the PreCompact drive does a better job when all of the files are kept together and there are no wholes. 

So I run this (on an old manchine that's not doing much else) before I shrink the disk files for archiving.

[jeroen]

I have confirmed with HDTune that there is no performance drop from the beginning of the virtual disk to the end, so it seems that there is no good reason to run with Optimize enabled.

Well, perhaps your virtual disks are so small that the speed differential between the beginning and the end of the virtual disk is negligeable. Or perhaps the virtual machine overhead is decreasing the speed below a point where the physical harddisk can easily keep up.

Optimization will still make your virtual disks faster, because of better seek times. The harddisk heads will have to travel less if all the files (inside the virtual disk) are placed close together. It's as simple as that.

[TimG]

Well, perhaps your virtual disks are so small that the speed differential between the beginning and the end of the virtual disk is negligeable...

This is what I presume as well. I imagine the RAID 10 may also play some role in this.

Optimization will still make your virtual disks faster, because of better seek times. The harddisk heads will have to travel less if all the files (inside the virtual disk) are placed close together. It's as simple as that.

That makes sense. Even across the RAID array, close proximity within each stripe should be helpful.

[elmo]

It seems to me that there is no good reason to run the Optimize phase inside these VMs. I have confirmed with HDTune that there is no performance drop from the beginning of the virtual disk to the end, so it seems that there is no good reason to run with Optimize enabled. So I have been running it with the "-a 2" option.

New JKDefrag user here - first time poster - great app!

Anyway, some VM's can have huge virtual disks, as big as a HDD from just several years ago.  And those big files can get fragged and span across an even bigger disk.  I have no benchmarks to show, but my defrag strategy is to defrag the VM's virtual disk first.  That orders the VD's contents.  Then I close the VM and defrag again from the host to get the VD defragged.  This seems to work for my fixed size VD's.  I think that'd work well for a dynamic VD too.  I think it'd be fine to reverse the order too, as either way would get em straighted out after a couple passes.  I still take the optimize approach on both sides though.  Anything to keep the heads from moving!   

[JamesOff]

I wrote quite a sizeable post on this subject previously: http://www.kessels.com/forum/index.php?topic=917.msg5541#msg5541

[TimG]

I just wanted to report that, in addition to trouble-free defragging inside the VMs, I've had good success with using JkDefrag on the VM hosts. I use the "-s 50" option, and users have not experienced any noticeable delays. Great program.