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Re: [Xen-users] Slow Disk access on SLES 10 install

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Slow Disk access on SLES 10 install
From: D Sims <dwains@xxxxxxxxx>
Date: Sun, 4 Mar 2007 17:57:30 -0800 (PST)
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Matthias:

You were 100% correct.  That was the piece of information that I did not
know that I needed.  As soon as I changed the setting in the
/etc/xen/scripts/block  script from

do_or_die losetup -y "$loopdev" "$file"

do_or_die losetup  "$loopdev" "$file"

this made all the difference in the world.  

However, this does beg another question. What is the best practice for
setting up a virtual disk for a guest domain?

Is it better to live with the possibility of data corruption on a host crash
and have normal disk access, or turn the flag on and be protected against
corruption, but suffer terrible performance.  Or is there a better way? 
Possibly to assign the guest domains their own disk partition that they can
write to as they please?  I have not tried this yet (I will tomorrow), but
that sounds like a better bet.  Or is there another way?

Thanks a ton for your help.

Dwain Sims





Hi,

it seems to me that you use a file for the disk,

>disk = [ 'file:/var/lib/xen/images/basesles10/hda,hda,w' ]

if you use a fresh SLES10 installation, you should read SLES10 Release
Notes:
http://www.novell.com/linux/releasenotes/i386/SUSE-SLES/10/RELEASE-NOTES.en.html
Theres a paragraph called: "Sync Mode for Loopback Storage" which could
help.

Hope this helps!

Regards,
Matthias


Am Samstag, den 03.03.2007, 05:20 -0800 schrieb D Sims:
> I have been struggling with a problem for a couple of days and I hope
> someone
> has some ideas.
> 
> I am using SLES 10 as a base for my Dom0 and I am trying to build a
> paravirtualized guest domain.  
> 
> I have tried lots of combinations of things but the disk during the
> install
> is increcdibly slow.  I am fairly certain that this is
> something I have set wrong, as I see the same results on two very
> different
> hardware platforms.  It takes about 2 hours for the first CD install; and
> that time is the same if I use the cd drive as a source of my install or
> if
> I use an NFS based source.
> 

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