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

[Heli <helicoterus-elih@xxxxxxxx>]

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 
> > read.
> > 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! 
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