On Thu, 02/25 08:49, Stefan Priebe - Profihost AG wrote: > > Am 22.02.2016 um 23:08 schrieb John Snow: > > > > > > On 02/22/2016 03:21 PM, Stefan Priebe wrote: > >> Hello, > >> > >> is there any chance or hack to work with a bigger cluster size for the > >> drive backup job? > >> > >> See: > >> http://git.qemu.org/?p=qemu.git;a=blob;f=block/backup.c;h=16105d40b193be9bb40346027bdf58e62b956a96;hb=98d2c6f2cd80afaa2dc10091f5e35a97c181e4f5 > >> > >> > >> This is very slow with ceph - may be due to the 64k block size. I would > >> like to check whether this is faster with cephs native block size of 4mb. > >> > >> Greets, > >> Stefan > >> > > > > It's hardcoded to 64K at the moment, but I am checking in a patch to > > round up the cluster size to be the bigger of (64k, > > $target_cluster_size) in order to make sure that incremental backups in > > particular never copy a fraction of a cluster. As a side-effect, the > > same round-up will happen for all modes (sync=top,none,full). > > > > If QEMU is aware of the target cluster size of 4MB, this would > > immediately jump the copy-size up to 4MB clusters for you. > > > > See: https://lists.nongnu.org/archive/html/qemu-devel/2016-02/msg02839.html > > Thanks for your patches and thanks for your great answer. But our > problem is not the target but the source ;-) The target has a local > cache and don't care about the cluster size but the source does not. > > But it works fine if we change the default cluster size to 4MB. So it > has point us to the right direction.
Does it mean overriding the copy granularity is what you want to do? Asking because drive-mirror has a "granularity" parameter for this purpose, if so it should probably be considered for drive-backup as well. Fam
