On Tue, Jun 07, 2016 at 07:30:19PM +0300, Vladimir Sementsov-Ogievskiy wrote: > On 03.06.2016 18:45, Denis V. Lunev wrote: > > On 06/03/2016 06:06 PM, Eric Blake wrote: > > > On 06/03/2016 08:05 AM, Vladimir Sementsov-Ogievskiy wrote: > > > > Add target-zeroed flag to allow user specify that target is already > > > > zeroed. With this flag set zeroes which was in source before mirror > > > > start will not be copyed. > > > With this flag set, any runs of zeroes in the source before the mirror > > > starts will not be copied. > > > > > > > Without this libvirt migration of empty disk takes too long time. > > > > > > > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> > > > > --- > > > > > > > > I've tested it with > > > > time virsh migrate --live test qemu+ssh://other_node/system > > > > --copy-storage-all > > > Presumably with a libvirt patch to turn on the optional flag. > > > > > > I'm not sure I like this patch. Libvirt uses NBD to implement > > > --copy-storage-all, I think we're better off improving NBD to > > > automatically handle sparse writes, than we are to add a one-off hack > > > that requires libvirt to change. That is, once NBD is smarter, the copy > > > will be faster without needing a tweak. And we ARE working on making > > > NBD smarter (one of my goals for the 2.7 release is to get all the > > > sparse file additions to NBD implemented) > > > > > > That said, I'll still review it. > > this is not enough, definitely. > > > > There is a problem that mirror_iteration code sleeps even for > > not read zeroes (and this IS slow). Moreover, even sending sparcified > > zeroes takes a lot of time for round trips. > > > > We have started with that and spent a lot of time trying to improve > > the situation. > > > > Also, as a side note, the QCOW2 file on a source and a target will > > be different without the flag - original image has empty blocks, > > target image will have blocks explicitly marked with zeroes. > > > > Though this is a matter of taste... For us this approach is the simplest. > > > > Den > > Hey, what do think about it? Don't we forget somebody to be cc'ed?
Jeff Cody <jc...@redhat.com> maintains block jobs. This patch should go through him. Stefan
signature.asc
Description: PGP signature
