Thanks! On Thu, Jun 3, 2021, 2:46 PM Nir Soffer <[email protected]> wrote:
> On Thu, Jun 3, 2021 at 8:47 PM Strahil Nikolov <[email protected]> > wrote: > > > > Hey Nir, > > > > you said that the data in the snapshot changed ? > > I always thought that snapshots are read-only. > > Indeed snapshot is ready only - until you start to delete it. This is > why we mark the > snapshot as illegal once delete snapshot was started. > > It works like this: > > 1. Before snapshot > > Snapshots: (none) > Volumes: A (active) > > A is read-write volume, changing while the vm is running. > > 2. After snapshot > > Snapshot: snap1 (disk snapshot A) > Volumes: A <- B (active) > > A is now read only image, will never change > B is read-write, modified by the vm > B backing file is A > > 2. Start delete snapshot 1 > > Snapshot: snap1 (disk snapshot A, illegal) > Volumes: A <- B (active) > > On the host running the vm, we perform block commit job, > copying data from B into A. > > When the job completes, A contains all data in B, and any new > data written to the B is mirrored to A. > > 3. Pivoting to volume A > > When the block commit has completed, we switch to vm to use volume A > instead of volume B. > > At this point the VM is writing again to volume A, and volume B is unused. > > Snapshot: snap1 (disk snapshot A, illegal) > Volumes: A (active) <- B > > 4. Cleanup > > On engine side, snapshot 1 is deleted > On the host, volume B is deactivated > On the SPM host, volume B is deleted > > Snapshot: (none) > Volumes: A (active) > > I hope this is more clear now. > > Nir > >
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