What is the CPU utilization when you did this I/O performance measurement?
As far I can remember, Bonnie++ does not support using outstanding I/Os.

performance.
Liang

To: "Xen-Users" <xen-users@xxxxxxxxxxxxxxxxxxx>
Sent: Tuesday, April 17, 2007 8:28 AM
Subject: [Xen-users] Big I/O performance difference between dom0 and domU

Hi,
I am setting up a dual CPU PowerEdge 2550 system with PERC 3Di
controller (aacraid) with 3 18GB disks in RAID5 and XEN 3.0.3-0-2,
credit scheduler, PAE (the Debian package in etch). This is not best
hardware, but what worries me more is the poor I/O performance in domU
compared to dom0.
With both domains having 500 MB of RAM, testing with bonnie++ on the
same 5GB LVM volume with xfs filesystem, with 4GB test data size, I'm
getting:
-----+-------------------+--------------------+-----------------------
Test | block read [kB/s] | block write [kB/s] | random seeks [/sec]
-----+-------------------+--------------------+-----------------------
dom0 | 10308 | 64806 | 325.3
domU | 7299 | 53469 | 265.6
-----+-------------------+--------------------+-----------------------
~drop| 30% | 17% | 18%
-----+-------------------+--------------------+-----------------------
The results are basically the same whether I use the default vcpu
arrangement (2 vcpus for dom0, one for domU) or set it to one vcpu per
domain, each pinned to a different physical cpu.
Any suggestions are welcome...
--
Marcin Owsiany <marcin@xxxxxxxxxx> http://marcin.owsiany.pl/
GnuPG: 1024D/60F41216 FE67 DA2D 0ACA FC5E 3F75 D6F6 3A0D 8AA0 60F4 1216
"Every program in development at MIT expands until it can read mail."
 -- Unknown
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