Is there a recommended solution for defragging disks on Windows guests in this type of environment? --- VSphere, ESXi, Version 5, using iSCSI SAN environment (both RDM and LUN to LUN utilized), Windows W2k3, W2k8 R2 guests
I have tested PerfectDisk and Diskeeper but this was using Local disk in a test environment (Equallogic 6500), on thick provisioned disks ONLY, don't use on thin provisioned, or linked clones.
Updates:
6/2012: Dell/Equallogic SANs - Do not use a Windows Guest Defragmentation utility if you use SAN Thin Provisioning unless you have the latest firmware (released in early 2012) for older model SANs, (PS6000, PS6500 and older).
4/4/2013:
This is a great article on this topic by Corman Hogan:
http://blogs.vmware.com/vsphere/2011/09/should-i-defrag-my-guest-os.html
In general - you typically do not need to use a Windows guest level defrag utility. If you use a SAN check with the vendor first. If you use Equallogic SAN, non SSD, Thick provisioned disks, and fragmentation is over 20% you might look at Diskeeper and/or Perfectdisk. They have VMWare features that prevent fragmentation from intially ocurring. EMC has low-level defrag built in, and so a guest level defrag util is not needed.