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[Xen-users] bad I/O performance with HP Smart Array RAID

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Subject: [Xen-users] bad I/O performance with HP Smart Array RAID
From: Thomas Aeby <aeby@xxxxxxxxxx>
Date: Tue, 24 Feb 2009 16:16:00 +0100
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Hi all,

I discovered lately that two of my XEN servers suffer from a really bad disk throughput - in domU as well as in dom0. All of them run Debian/Etch, Kernel 2.6.18-6-xen (orig. Debian) with XEN 3.2 (backported). The software versions seem to be ok for most machines:

 Lenovo A57 with S-ATA and (E8200, VT enabled): up to 90MB/s
 Shuttle, FB61 based, ATA-Disk (Celeron, no VT): up to 55MB/s
 HP ML350 G5, Smart-Array RAID-Controller (E5420, VT enabled): ~12MB/s
 IBM x3650, ServeRaid 8k RAID-Controller (E5405, VT enabled): ~140MB/s

The figures are not real benchmarks - just a dd of a file which is big
enough to get around cache effects in dom0.

Unfortunately, the HP machines with the problem are in production use so
that I cannot confirm, but I usually get normal performance out of HPs
with SmartArray controllers and non-Xen kernels. I'll go for a
maintenance window in a few days to do some testing with a non-XEN
kernel on them.

I have seen other posts on the list having problems that smell similiar with other hardware - but no solution.

Is there anything I could try to find out what the problem is? Any hint
on what I could try? Even a "of course, the driver for SmartArray does not
perform well" would help.

Best regards,

Thomas Aeby, Kirchweg 52, 1735 Giffers, Switzerland
Voice : (+41)26 4180040
Internet: aeby@xxxxxxxxxx                       PGP public key available

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