[CentOS-virt] Storage performance

Hi, I recently did some benchmarking on a Rackspace VM and was surprised that bonnie++ showed a read throughput of almost 500MB/sec. Does anyone have an idea how they achieve these speeds in a shared environment? While you can achieve this with a RAID easily these days once you have lots of VMs accessing that array I would expect that speed to go down quite a bit. Was I just lucky that I was the only one accessing the disks that way at that moment or how do they keep up with this kind of demand?

Regards, Dennis