I've been reading multiple threads on this topic but I think I am missing something here. There are several threads encouraging people to defrag their ESX guests. How does this improve performance?
My understanding of DEFRAG is that it moves blocks around on your disk in order to increase performance. ie. My file sits in 9 blocks sitting across the disk in random locations. Defrag would move these 9 blocks to create 9 contiguous blocks on the spindle. This allows the disk arm to move less, thus improving performance on the disk.
On ESX this is highly abstracted from the guest. The guest thinks the files are sitting all over the disk. So it moves the blocks all around to increase performance. The problem is that the guests is mapping data to blocks on a virtual scsi disk (vmdk). This has nothing to do with the actual block placement on your SAN. There is no way for the virtual guest to see contiguous blocks on physical spindles sitting on a san is there? If not, isn't defrag within a guest pointless?