Re: [Xen-devel] Re: [PATCH v3] xen block backend.

[Christoph Hellwig]

On Thu, Apr 21, 2011 at 08:28:45AM +0100, Ian Campbell wrote:
> On Thu, 2011-04-21 at 04:37 +0100, Christoph Hellwig wrote:
> > This should sit in userspace.  And last time was discussed the issue
> > Stefano said the qemu Xen disk backend is just as fast as this kernel
> > code.  And that's with an not even very optimized codebase yet.
> 
> Stefano was comparing qdisk to blktap. This patch is blkback which is a
> completely in-kernel driver which exports raw block devices to guests,
> e.g. it's very useful in conjunction with LVM, iSCSI, etc. The last
> measurements I heard was that qdisk was around 15% down compared to
> blkback.

Please show real numbers on why adding this to kernel space is required.

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