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Re: [Xen-users] Difference performances between HVM and PV guest in hard

Subject: Re: [Xen-users] Difference performances between HVM and PV guest in hard disc reading
From: Heli <helicoterus-elih@xxxxxxxx>
Date: Sat, 30 May 2009 19:20:14 +0200
Cc: "Fajar A. Nugraha" <fajar@xxxxxxxxx>, xen-users list <xen-users@xxxxxxxxxxxxxxxxxxx>
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Fajar A. Nugraha wrote:
On Sun, May 24, 2009 at 7:25 PM,  <helicoterus-elih@xxxxxxxx> wrote:
I perform some tests to get hard disc performance differences between HVM domU 
and a paravirtualized one (both Debian Lenny).

I used hdparm ( option -t and -T) to test cache of disc and disc sequential 
Syntax is:
hdparm -t|-T /dev/hda1

hdparm -t for hvm returns about 30 MB/sec, wheras hdparm -t for PV return about 
180 MB/sec.

This is normal. HVM by default should have MUCH lower disk throughput.
That's why HVM domUs need PV drivers for both Linux (included by
default on RHEL/Centos 5.3, not available yet for newer kernels) and
Windows (like GPLPV).

hdparm -T for hvm returns about 1247 MB/sec, wheras hdparm -T for PV return 
about 1183 MB/sec.

-T is cached result. Repeat this several times and you should find
similar output for both PV and HVM.

How is it possible that a PV domU returns 180 MB/sec if on a normal linux hdparm returns 45 MB/sec?

So PV is very crazy!!!Chiacchiera con i tuoi amici in tempo reale! http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com
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