[CentOS-virt] io writes very slow when using vmware server

Paul Bijnens Paul.Bijnens at xplanation.com
Tue Oct 7 08:26:47 UTC 2008

On 2008-10-06 10:39, Pasi Kärkkäinen wrote:
> On Sun, Oct 05, 2008 at 11:28:45AM +0200, Paul Bijnens wrote:
>> We are struggling with a strange problem.
>> When we have some VMWare clients running (mostly MS windows clients),
>> than the IO-write performance on the host becomes very bad.
>> The guest os's do not do anything, just having them started,
>> sitting at the login prompt, is enough to trigger the problem.
>> The host has plenty of 4G of RAM, and all clients fit easily into
>> the space.
>> The disksystem is a RAID5 (ok, not the fastest choice).
>> Both hosts are running the latest CentOS 5.2 (but the problem was
>> already present in 5.0 as well), and running the latest production
>> version of VMWare server 1.0.7 (but when running 1.0.5 the problem
>> was there too).
> Hello.
> I assume you know VMware server v1.x is not supported on RHEL5/CentOS5.. 
> Have you tried VMware server v2.0?

You wouldn't believe now many times i've checked to see if 2.0 was
in production.  I did not verify before sending this mail.

Also, because it was rather difficult to test beta software on these
servers (only limited time in the weekends were free to test variations
in the setup), I did not try to run 2.0beta.

To my surprise indeed 2.0 is now out of beta indeed. I installed it,
and indeed, it works!  No performance loss, even with 4 VM guests

Case closed.

> 20 MB/sec sounds really bad. There has to be something wrong with your
> raid/disk setup.

I don't believe 20MB/s sustained write performance is too bad for RAID5
with 4 sata disks, in a inexpensive machine.  Do you do much better?

Paul Bijnens, xplanation Technology Services        Tel  +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM    Fax  +32 16 397.512
http://www.xplanation.com/          email:  Paul.Bijnens at xplanation.com
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