And then you notice this…
Our recent Senior Infrastructure Engineer hire was remarking today how one of the LUNs on our EMC storage array was hitting 100% utilization in the middle of the night. At first glance, everyone thought this was the LUN for our data warehouse. After digging further, it turned out the LUN housed the development environments for our new platform.
So, what was occurring in the middle of the night for the LUN to see 100% utilization?
Disk defrag.
To get a better grasp of our development environment, we have one VM in Lab Manager that gets assigned to different users. Each copy of this VM was trying to defrag it’s disk at the same exact time. If you understand how Lab Manager and link clones work, you can understand why this was quickly disabled.
Ah, the joys of work. Yes this blog post was short, and hopefully I’ll post more in the future about my recent tasks of setting up Nexus 5020 and Nexus 1000v, both awesome products.
Geaux Virtual 
Speaking for NetApp we have advocated for many years that there is no need to defragement the fiel system of SAN connect hosts. This practice is also repeated with VMs as realigning file system blocks in a VMDK has the same impact of doing so in a LUN.
I cover some of the negative impacts of running defrag in a GOS in my thin provisioning posts on http://blogs.netapp.com/virtualstorageguy/.
I realize your environment, or at least some portion of it, runs on EMC storage; however, I would be surprised if they don’t have the same recommendations.
Vaughn Stewart
January 6, 2010 at 8:06 am
We normally do not defrag our VMs. This special VM was created by a consultant who set up this scheduled task on his own without informing us.
jguidroz
January 6, 2010 at 9:22 am