Am 28.02.24 um 17:24 schrieb Vladimir Sementsov-Ogievskiy: > On 16.02.24 13:55, Fiona Ebner wrote: >> Previous discussion from when this was sent upstream [0] (it's been a >> while). I rebased the patches and re-ordered and squashed like >> suggested back then [1]. >> >> This implements two new mirror modes: >> >> - bitmap mirror mode with always/on-success/never bitmap sync mode >> - incremental mirror mode as sugar for bitmap + on-success >> >> Use cases: >> * Possibility to resume a failed mirror later. >> * Possibility to only mirror deltas to a previously mirrored volume. >> * Possibility to (efficiently) mirror an drive that was previously >> mirrored via some external mechanism (e.g. ZFS replication). >> >> We are using the last one in production without any issues since about >> 4 years now. In particular, like mentioned in [2]: >> >>> - create bitmap(s) >>> - (incrementally) replicate storage volume(s) out of band (using ZFS) >>> - incrementally drive mirror as part of a live migration of VM >>> - drop bitmap(s) > > Actually which mode you use, "never", "always" or "conditional"? Or in > downstream you have different approach? >
We are using "conditional", but I think we don't really require any specific mode, because we drop the bitmaps after mirroring (even in failure case). Fabian, please correct me if I'm wrong. > Why am I asking: > > These modes (for backup) were developed prior to > block-dirty-bitmap-merge command, which allowed to copy bitmaps as you > want. With that API, we actually don't need all these modes, instead > it's enough to pass a bitmap, which would be _actually_ used by mirror. > > So, if you need "never" mode, you just copy your bitmap by > block-dirty-bitmap-add + block-dirty-bitmap-merge, and pass a copy to > mirror job. > > Or, you pass your bitmap to mirror-job, and have a "always" mode. > > And I don't see, why we need a "conditional" mode, which actually just > drops away the progress we actually made. (OK, we failed, but why to > drop the progress of successfully copied clusters?) > I'm not sure actually. Maybe John remembers? I see, I'll drop the 'bitmap-mode' in the next version if nobody complains :) > > Using user-given bitmap in the mirror job has also an additional > advantage of live progress: up to visualization of disk copying by > visualization of the dirty bitmap contents. > Best Regards, Fiona
