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Re: [Xen-users] Windows Disk performance

To: James Harper <james.harper@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Windows Disk performance
From: Ruslan Sivak <russ@xxxxxxxxxx>
Date: Sat, 07 Jun 2008 12:29:06 -0400
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James Harper wrote:
I've been getting disappointing results on IO reads when using windows
guests.  I'm getting usually around 70MB/s reads using hdtune.  When
installing James' PV drivers, the speed drops to about 20MB/s.

The host system is getting around 350MB/s reads.  I'm wondering if
there
is such a significant slowdown, or if my tests are somehow flawed.
The
70MB/s persisted throughout my VM testing, whether I was using Xen,
XenSource or VMWare Server.

So my questions are:

a.  Is there a bottleneck somewhere which basically caps the windows
disk performance?
b. Is my testing methodology flawed.  Is there a better windows tool
that will measure performance?  What about Linux tool?  I'm currently
using hdparm -t

If you are using the same tool in Windows then I'm comfortable that a
drop from 70MB/s to 20MB/s indicates a major problem somewhere.

Actually, since I haven't implemented any of the event log stuff yet as
per my last email, could you run DebugView from sysinternals and see if
any logging comes up while you run your performance tool? Make sure
kernel logging is on - you can tell if it is if you go into disk
management and a whole lot of debug info gets output.

James

_______________________________________________

I will try this on Monday. Do you know how to turn kernel logging on if it's not? This thread was actually more about why I'm getting such poor perceived performance under the stock drivers. I understand that there may be some issues to work out with the PV drivers, but I wouldn't have expected such a huge hit of performance across the board with the stock drivers (And across the board I mean, Xen, XenServer and VMWare). Should I try testing with something like IOmeter? I'm really more interested in db type performance, so maybe a real benchmarking package is necessary. You know the kind that Tom's Hardware uses to measure performance? Does anyone know of any good ones?

Russ

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