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Re: [Xen-users] write through or write back?

To: Lei Lu <lulei.wm@xxxxxxxxx>
Subject: Re: [Xen-users] write through or write back?
From: Pasi Kärkkäinen <pasik@xxxxxx>
Date: Tue, 23 Nov 2010 21:23:13 +0200
Cc: xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
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On Mon, Nov 22, 2010 at 12:18:13PM -0500, Lei Lu wrote:
> Hi everyone,
> Can anybody clarify about what disk cache mechanism the current Xen
> hypervisor use? is it write through or write back? Is there a way to
> change between this two modes? As far as I know, the original linux
> kernel implements the disk cache as page cache and the flusher thread
> may periodically flush the dirty pages to the disk. Does Xen still use
> this strategy by default or not?


Actually Xen *hypervisor* itself doesn't affect this..
it depends on your dom0 setup.. ie. what disk backend you 
choose for the guest vm virtual disks.

file: backed disks use dom0 linux kernel caching, 
but tap:aio: or phy: backed disks don't..

-- Pasi

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