[dm-devel] ANNOUNCE: SCSI XCOPY support for the kernel and device mapper

Mikulas Patocka mpatocka at redhat.com
Tue Jul 15 19:26:10 UTC 2014

On Tue, 15 Jul 2014, Christoph Hellwig wrote:

> On Tue, Jul 15, 2014 at 02:33:13PM -0400, Mikulas Patocka wrote:
> > Hi
> > 
> > I annouce that I released the first version of a patch set that makes it 
> > possible to use SCSI XCOPY offload for the block layer and device mapper.
> > 
> > The patchset is at 
> > http://people.redhat.com/~mpatocka/patches/kernel/xcopy/series.html It 
> > requires kernel version at least 3.16-rc4. It was tested on target-core 
> > iSCSI implementation.
> Can you send the series to the mainling list(s)?  That makes it a lot
> easier to do a quick review.

I'll post them to the lists.

> > The dm-kcopyd subsystem is modified to use the XCOPY command, so device 
> > mapper targets that use it (mirror, snapshot, thin, cache) take advantage 
> > of copy offload automatically.
> That sounds good, do you have any benchmarking data that shows the
> advantage of using XCOPY?

dm-mirror resynchronization is 4 times faster with XCOPY offload, but it 
is just a benchmark on a network with iSCSI between two slow machines.

I hope that we get some benchmarks on a real hardware.


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