VMware for Cyrus?

[Adam Tauno Williams]

On Mon, 2009-11-09 at 08:55 -0300, Reinaldo de Carvalho wrote:
> On Mon, Nov 9, 2009 at 8:43 AM, Sebastian Hagedorn
> <Hagedorn at uni-koeln.de> wrote:
> > --On 9. November 2009 08:37:46 -0300 Reinaldo de Carvalho
> > <reinaldoc at gmail.com> wrote:
> >> You need analyse the I/O consumition.
> >> # iostat -d 1
> > I trust real world experiences more than benchmarks ... either people on
> > this list have successfully run Cyrus under ESX or they haven't. I don't
> > want to be the first to try it.
> A lower I/O consumition should always to work fine in virtualization.

"Lower" than what?  This statement is meaningless.

We run a ~500-600 connection Cyrus in ESX.  But that isn't ~2,500.
There are so many variables here.

How much I/O your hypervisor can absorb depends on the same thing as a
metal system - the underlying I/O subsystem.  So far with ESX I've seen
that the I/O subsystem bottlenecks before there is any 'hard limit' in
the hypervisor;  just like a metal system bottlenecks before any 'hard
limit' in a [modern/recent] OS.  The real problem with virtualization is
that it becomes almost trivial to over-subscribe the system,  it works
great so long as only a few systems load spike at once - when seven or
eight servers load spike at the same time things get ugly and the poor
sys-admin's cell phone gets inundated with SMS alerts.