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Re: [Xen-devel] [patch] Add support for barriers to blk{back,front} driv

To: Gerd Hoffmann <kraxel@xxxxxxx>
Subject: Re: [Xen-devel] [patch] Add support for barriers to blk{back,front} drivers.
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 09 Nov 2006 13:47:36 +0000
Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On 9/11/06 12:48, "Gerd Hoffmann" <kraxel@xxxxxxx> wrote:

>> What happens (even on native Linux) if you have, say, a RAID array in which
>> some of the discs support barriers and others don't?
> 
> The raid0 driver doesn't support barriers in the first place.  Not sure
> about the other raid drivers.

Does this mean journalling filesystems cannot run reliably on top of RAID-0?
That sounds a bit concerning!

What about when running on top of LVM, where an LV is stitched together from
bits of various PVs. Some may support barriers, some may not. Running on top
of LVM is default for most distros, so surely it must have a story on write
barriers?

 -- Keir



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