On Mon, Aug 12, 2013 at 06:56:33PM +0800, Liu Yuan wrote: > On Mon, Aug 12, 2013 at 09:54:59AM +0200, Valerio Pachera wrote: > > After I've been taking the snapshot of vdi 'backup', write speed went > > from 15 to 6/7 M/s and it doesn't change even if I rewrite multiple > > times a file. > > I also tried to remove the snapshot and rewrite the same file several > > time and the speed is still 6/7 M/s (except once). > > Am I misunderstanding 'only first write will be slowed down'? > > > > No. It seems something goes wrong. I'll check it. I can't reproduce the issue on my laptop. I tried -drive file=sheepdog:test,if=virtio -drive file=sheepdog:test2,if=virtio to start VM, and dd these two vdis. Name Id Size Used Shared Creation time VDI id Copies Tag s test 1 200 MB 200 MB 0.0 MB 2013-08-12 19:23 7c2b25 1 tag test 0 200 MB 0.0 MB 200 MB 2013-08-12 19:23 7c2b26 1 test2 0 200 MB 200 MB 0.0 MB 2013-08-12 19:23 fd3815 1 You can see that test is a vdi with objects shared with 'snapshot test', test2 is a normal vdi. I got almost the same performance for test and test2 by dd if=/dev/zero of=/dev/vdx bs=1M count=100 oflag=direct. Thanks Yuan |