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RE: [Xen-users] Partition vs disk images

To: "Fajar A. Nugraha" <fajar@xxxxxxxxx>, "Xen Users" <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] Partition vs disk images
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Tue, 29 Apr 2008 16:16:50 +1000
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Thread-topic: [Xen-users] Partition vs disk images
> > But is there really a performance difference between LVM & file
> > VM's?
> >
> Yes, but depending on how you use it, the effect might not be what you
> expect.
> Example 1 :
> - you have 16G mem : 4G for domU, 12 G for dom0
> - 1 domU running, with 4G root filesystem
> In this scenario, you'd most likely find file-based VM perform better
> since dom0 will cache domU's root fs.

No this should not happen! Under HVM it did, and maybe still does, but
it's bad! It means that writes that DomU _thinks_ have been committed to
disk may not have been, and really bad things can happen. Do you know
for sure that file: based devices use Dom0's page cache?


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