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Re: [Xen-users] poor I/O performance with PV drivers and I/O emu

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Subject: Re: [Xen-users] poor I/O performance with PV drivers and I/O emu
From: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Date: Wed, 15 Apr 2009 16:28:53 +0700
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On Wed, Apr 15, 2009 at 2:36 PM, Riccardo Veraldi
<Riccardo.Veraldi@xxxxxxxxxxxx> wrote:
> I am using a physical partition and exporting the disk as a xvda disc on the
> domU.
> The domu can see the disk as a xvda.
> So I did a test with bonnie++ and I got the same poor results as I have with
> Am I missing something in the configuration or the performances are so poor
> also
> using PV drivers for disk IO ?? is this normal ?

Are you SURE domU actually USE xvda?
Last time I check, by default both ide driver (or whatever driver
handles the default IOEMU disk) and xen-vbd will detect the disk,
resulting it to be detected TWICE as hda AND xvda. If you use LVM on
domU, it uses the first device it sees (hda), which would explain the
bad performance.

You might want to try :
- assign new disk as xvdf
- partition and mount that disk on domU (without using LVM)
- run bonnie++ on that disk

If it gives good result, I can tell you later how to make ide driver
ignore the disk. If it still gives bad result, my guess is something
else is wrong with your setup.



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