Re: [Xen-users] Xen DomU with high IOWAIT and low disk performance (lvm raid1)

[Andreas Nitsche <andi@xxxxxxxxx>]

Hello,

Problem is solved.

After removing the sync option the partition in DomU is really fast. ~33
MB/s writing.

-- 
Andi

Am Donnerstag, den 03.12.2009, 08:46 +0100 schrieb Andreas Nitsche:
> Hello list!
> 
> My setup:
> 
> Dom0: Debain 5.0.3 with xen-hypervisor-3.2-1-i386 (2.6.26-2-xen-686)
> DomU: Ubuntu 8.04 2.6.26-2-xen-686
> 
> System is running on two hard drives mirrored with raid1 and organized
> by LVM. Dom0 and DomU are running on logical volumes.
> 
> Partitions for DomUs are connected via 'phy:/dev/lvm/disk1,sda1,w' for
> example.
> 
> Here are some scenarios I testet, where you should easily can see that
> DomU is much much slower than Dom0 when having read and write access at
> the same time on the harddrive.
> 
> dd if=/dev/zero of=test.img bs=1M count=1000
> Dom0:
> $ dd if=/dev/zero of=test.img bs=1M count=1000
> 1000+0 DatensÃtze ein
> 1000+0 DatensÃtze aus
> 1048576000 Bytes (1,0 GB) kopiert, 12,88 s, 81,4 MB/s
> DomU:
> $ dd if=/dev/zero of=test.img bs=1M count=1000
> 1000+0 DatensÃtze ein
> 1000+0 DatensÃtze aus
> 1048576000 Bytes (1,0 GB) kopiert, 16,8728 s, 62,1 MB/s
> 
> 
> dd if=test.img of=/dev/null
> Dom0:
> $ dd if=test.img of=/dev/null
> 2048000+0 DatensÃtze ein
> 2048000+0 DatensÃtze aus
> 1048576000 Bytes (1,0 GB) kopiert, 5,47333 s, 192 MB/s
> DomU:
> $ dd if=test.img of=/dev/null
> 2048000+0 DatensÃtze ein
> 2048000+0 DatensÃtze aus
> 1048576000 Bytes (1,0 GB) kopiert, 10,2963 s, 102 MB/s
> 
> Reading and writing from and to the hard drives works fast.
> 
> date; cp test.img test2.img; date
> Dom0:
> $ date; cp test.img test2.img; date
> Do 3. Dez 08:22:44 CET 2009
> Do 3. Dez 08:22:57 CET 2009
> 
> ~76,92 MB/s
> 
> DomU:
> $ date; cp test.img test2.img; date
> Do 3. Dez 07:23:16 UTC 2009
> Do 3. Dez 07:28:24 UTC 2009
> 
> ~3,25 MB/s
> 
> date; mv test.img /backup/; date
> Dom0:
> $ date; mv test.img /backup/; date
> Do 3. Dez 08:28:45 CET 2009
> Do 3. Dez 08:28:58 CET 2009
> 
> ~76,92 MB/s
> 
> DomU:
> $ date; sudo mv test.img /backup/; date
> Do 3. Dez 07:31:15 UTC 2009
> Do 3. Dez 07:36:16 UTC 2009
> 
> ~3,32 MB/s
> 
> /backup is a second logical volume inside the same lvm.
> 
> Each test was made time by time, so no process was running which
> produces high io at testing time.
> 
> My question: Why is DomU that slow on read and write access at the same
> time? And how can I get that faster?
> 
> _______________________________________________
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> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users


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