[ Thanks to Amy Newman for this link.
]
“Storage planning for virtualized systems requires some careful
thinking about the issues that will impact users. One major
tradeoff of virtualizing systems is that you are trading local
bandwidth for network bandwidth. In a nonvirtualzaed environment,
each user has local storage for at least booting his system and
very often for his data as well. On a virtualized system, the user
boots up over the network and accesses applications and data over
the network. Here, network performance and, more importantly,
network latency is critical. We all know that the seek+latency on a
standard enterprise SATA drive is around 4.16 ms for seek and
between 8.5ms (read) and 9.5ms (write) depending on the drive
manufacturer. This is not going to change, so latency must be
considered.”