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[Xen-users] Software RAID in DomU - does it work?

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Subject: [Xen-users] Software RAID in DomU - does it work?
From: Anthony Wright <anthony@xxxxxxxxxxxxxxxxx>
Date: Thu, 24 Aug 2006 14:54:24 +0100
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I'm playing around with a file server as a Xen DomU, and as part of that I'd like to implement software RAID on the disks. From an architectural point of view, I'd like to keep all the file system components within the DomU.

I'm looking at taking the raw disks (/dev/hd?? & /dev/sd??) from Dom0 piping them through to DomU as vbds, and then implementing software RAID on top of these vbds within the DomU.

This makes a lot of sense architecturally, but I'm concerned that there may be an additional layer of write buffering going on in Dom0 which will be invisible to the software RAID in DomU, but which may cause data to be written to the physical disk in a different order to that expected by the software RAID with the effect that it breaks the software RAID.

It's a bit hard to test this, so I wondered if anybody knows a little more about how the disk writes are processed in Dom0, whether they are buffered and whether this would have any effect on software RAID.

Thanks,

Tony Wright

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