[Beowulf] clustering using xen virtualized machines  Tim Cutts
tjrc at sanger.ac.uk Tue Jan 26 05:24:33 PST 2010  On 26 Jan
2010, at 12:00 pm, Jonathan Aquilina wrote:  > does anyone have
any benchmarks for I/O in a virtualized cluster?  I don't have
formal benchmarks, but I can tell you what I see on my   VMware
virtual machines in general:  Network I/O is reasonably fast -
there's some additional latency, but   nothing particularly
severe.  VMware can special-case communication   between VMs on
the same physical host, if required, but that reduces
flexibility in moving the VMs around.  Disk I/O is fairly poor,
especially once the number of virtual   machines becomes large.
This is hardly surprising - the VMs are   contending for shared
resources, and there's bound to be more   contention in a
virtualised setup than in physical machines.  In our case (~170
virtual machines running on 9 physical servers, each   of which
has dual GigE for VM traffic and dual port fibrechannel)
Forgive me for using VMware p