On 08/15/2011 10:51 PM, Nico Kadel-Garcia wrote:
> On Mon, Aug 15, 2011 at 6:05 PM, Orion Poplawski<[log in to unmask]>  wrote:
>> I have a server that I recently migrated from CentOS 5.6 to SL6.1.  The host
>> install serves as a basic disk server and runs our nightly backups with
>> amanda.  We also have several virtual machines running on it, so of which
>> are mostly idle and others which can be quite busy.  Since making the move
>> I'm seeing the disk and network response/performance go to hell if I have
>> any non-idle VMs running.  One barometer - I have a raid10 rebuild running
>> at the moment.  With no VMs I can reach 200,000K/sec resync speed.  I'm
>> getting 131,000K with two idle VMs and some other basic activity.  If I
>> start a busy vm, it drops to a few hundred K/sec and all disk access is very
>> slow. Response to keystrokes in a network shell can be very slow as well.
>>
>> As anyone else experienced problems like this?  I'm not seeing any error
>> messages on the host or VMs.
>
> Have you rebuilt the virtual images? And does the underlying RAID, and
> the disks, have 4096 byte blocks? If so, you will need to be quite
> cautious in partitioning your disk images, because no installer in the
> world can tell from scratch, inside a virtualized host, what the block
> size is on the underlying hardware, and this can *kill* your
> performance if it's mis-set.

Nope, everything is as before - I installed SL6 into the existing volume group 
and preserved the VMs logical volumes.  Thanks for the heads up though.


-- 
Orion Poplawski
Technical Manager                     303-415-9701 x222
NWRA/CoRA Division                    FAX: 303-415-9702
3380 Mitchell Lane                  [log in to unmask]
Boulder, CO 80301              http://www.cora.nwra.com