VMware for Cyrus?

[Simon Matter]

> Thanks for your reply!
>
> --On 9. November 2009 07:24:22 -0500 Adam Tauno Williams
> <awilliam at whitemice.org> wrote:
>
>> We run a ~500-600 connection Cyrus in ESX.  But that isn't ~2,500.
>> There are so many variables here.
>
> True ...
>
>> How much I/O your hypervisor can absorb depends on the same thing as a
>> metal system - the underlying I/O subsystem.
>
> We have a 2 Gbit IBM SVC-SAN connected with Fibrechannel over Cisco MDS
> 9509 switches. So far that's been sufficient, but we will probably upgrade
> that as well in the forseeable future. We will use the same SAN devices as
> raw devices under VMware. I've successfully done that on test
> installations.
>
>>  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,
>
> Exactly.

While virtualization has advantages it has also disadvantages. One thing
is that it introduces an additional layer of complexity into the game.
It's my impression that in many areas virtualization gets introduced not
because of technical reasons but because of political pressure.

For a high power, mission critical system like a mail cluster I'd stick
with real iron as long as possible. That may sound old fashioned but is
what I would do after everything I've seen. You will need the irons
anyway, with or without virtualization. Did I miss something?

Regards,
Simon

>
>>  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.
>
> So the real task would be to define appropriate reservations. But it's
> good
> to know that someone actually uses such a system in production, even
> though
> it's lower-sized than ours.
> --
>      .:.Sebastian Hagedorn - RZKR-R1 (Gebäude 52), Zimmer 18.:.
>                  .:.Regionales Rechenzentrum (RRZK).:.
> .:.Universität zu Köln / Cologne University - ✆
> +49-221-478-5587.:.----
> Cyrus Home Page: http://cyrusimap.web.cmu.edu/
> Cyrus Wiki/FAQ: http://cyrusimap.web.cmu.edu/twiki
> List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html