[LINK] Knight of razor to slash government spending

[Glen Turner]

Kim Holburn wrote:
> 
> You can save servers by using virtualisation, and they probably should 
> any way, lots of advantages.

I feel a rant coming on.

I've yet to see a virtualised environment which works as it should.

Partly that's because it forces capacity planning at a detailed
level, and we haven't done that since the days of mainframes.  How
many bytes of memory per Exchange mailbox? Per client connection?
It's just not in vendor documentation.

So the memory of the virtualised environment is a guess. It's got to
be a close guess or the savings from virtualisation disappear. So
half the time the guess it too low and the virtualised service sucks.

Partly it's because of insufficient disk I/O. That's a result of the
huge size of today's disks. People won't split a 10GB database across
six disks, even if six spindles are what is needed to meet the peak
I/O demand. And if you do use that many spindles, again your savings
from virtualisation disappear.

Sure, virtualisation has its uses. A production environment requires
a huge number of supporting servers -- development, system test, etc --
and combining these can achieve savings since those machines are
very underutilised. But for any hefty or critical production application
I'd stay well away from it until it becomes more mature about resource
allocation.

-- 
  Glen Turner