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[Xen-devel] blkback in DomU

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Subject: [Xen-devel] blkback in DomU
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Sun, 3 Oct 2010 00:41:32 +1000
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Thread-index: ActiP+fO9XZ1p1YaR+uoCt/PiyFLUQ==
Thread-topic: blkback in DomU
Is exporting a block device from one DomU to another supported? 'xm
block-attach' appears to support it based on the command line options
displayed but maybe it's one of those things that doesn't work because
nobody ever uses it?

I'm wondering about accessing a VSS snapshot from a windows DomU in Dom0
(or another DomU). In theory, GPLPV should be able to export the VSS
snapshot volume (assuming it exists as a block device in windows which
I'm not completely sure about...) back to Dom0 as a block device where
Dom0 can mount it (ntfs-3g etc). The IO request would go "Dom0 -> DomU
-> VSS mapping -> Dom0 -> physical device" which is a bit convoluted but
performance isn't necessarily the goal here so maybe it's not an issue.

If all of the above is possible, are there any back<->front issues with
DomU shutting down (or crashing) while Dom0 (or another DomU) has the
block device open or does xend tear it all down nicely?



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