Subject: Re: [vserver] tcpdump, top, mpstat, iostat
From: Christian Balzer <chibi@gol.com>
Date: Fri, 7 Jan 2011 14:19:14 +0900

On Fri, 7 Jan 2011 12:46:27 +0900 Andrej van der Zee wrote:

> > yes, but would be a waste of resources (to have a
> > separate device for each guest).
> 
> Yes true, but in terms of performance i would rather not have to guests
> competing for one disk head in particular for disk intensive apps such
> as a database server.
> 
That, like many things "depends", but unless all of your guests are I/O
bound all of the time a shared resource will be faster.
Take this example:
Given that are 8 disks in this example system the best degree of I/O
separation achievable would limit you to 8 Vserver guests. Now that also
leaves you with 8 single points of failure, but lets ignore that for the
moment (but not real life! ^o^). 
Say one of your guests is indeed a busy DB application, the others do
random, but not constant heavy I/O.
The single disk assigned to the DB guest will of course never be anywhere
near as fast as a RAID comprised of all the 8 disks (preferably a RAID10,
but even RAID5 would be faster).

Regards,

Christian
-- 
Christian Balzer        Network/Systems Engineer                
chibi@gol.com   	Global OnLine Japan/Fusion Communications
http://www.gol.com/