Re: [Xen-users] Xen Partition Performance

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

File backed VBDs can have pretty poor performance in some cases.  Also you 
*mustn't* put a ReiserFS filesystem into a file which is stored on a ReiserFS 
filesystem in the host.  It may break when you fsck the host [1]

LVM is probably the best compromise of flexibility / performance and should be 
pretty much as fast as partitions whilst being a lot more manageable.  You 
can also snapshot guest disks using it but be careful - snapshots don't scale 
that well if you use them long term and can run out of RAM.

Cheers,
Mark

[1] ReiserFS fsck looks for Reiser superblocks on the disk, in case they've 
got lost or something.  If you're fsck-ing dom0's filesystem using 
fsck.reiserfs and it finds the superblock from a domU filesystem there, it'll 
assume there's corruption and then proceed to do horrible things.  Don't go 
there.

On Tuesday 25 April 2006 13:47, Sylvain Coutant wrote:
> > I'm setting up a Xen system since I have diferent choices to
> > create the domU's partitions: raw partition, lvm, files.
> >
> > I've done some tests with hdparm and it all seems to be the same.
>
> It can if you have enough CPU in dom0. The interesting point could then be
> : how much each of those cost in CPU share in dom0 ? The less layers you'll
> have, the better it should behave. Raw partition should be the cheapest,
> closely followed by LVM and lastly files (which could have different
> results depending on fs in use: ext2, ext3, reiser, xfs, etc.). I'm not
> sure if the difference would be very significant. Probably, it depends on
> usage, number of domUs, ...
>
> BR,
>
> --
> Sylvain COUTANT
>
> ADVISEO
> http://www.adviseo.fr/
> http://www.open-sp.fr/
>
>
>
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-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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