Sudden (and apparently permanent) drop in disk performance
I am running ESXi 5.0 (free version, also why is there no forum for versions post 3.5?) on an HP Proliant Microserver N36L. I currently have two virtual machines, one running XP and another running Server 2003. The server VM is set up as a file server, using two virtual disks each taking up virtually all of a local 2TB hard drive (one is the primary data store, the other is backup). All drives are using PVSCSI.
However, during setup of the system and creating the initial backup from the primary to the backup drive within the VM, I encountered a sudden drop in IO performance (after around 220GB of data had been coppied), from ~40MB/s to ~4MB/s. Despite shutting down and re-starting the VM and even rebooting the host, I have not been able to recover the previous performance level. The performance did increase slightly, to around ~4.5MB/s after the VM was rebooted.
Does anybody have any idea what's going on here and how I can fix it? 4MB/s is very slow and not really acceptable for a file server with ~600GB of data on it!
I have attached the graphs of what happened, taken from VSphere Client.