I need to update/sync cold and hot standby containers on separate machines efficiently and I realized that lxc copy --refresh can’t help here because rsync is used in the refresh case and this can be very slow (slower than an initial full copy).
So I scripted the following files for an incremental ZFS snapshot send / receive to a backup server. In my tests the snapshot sync even worked with a running target container that finally is restored to the newly synchronized snapshot. This sync’ed container intentionally does not include further snapshots that are created on the source machine.
Now I’d like to discuss the completeness and relative stability of this approach regarding LXD updates as well as future simplifications e.g. remove the direct execution of zfs send on the remote source machine / switch over to lxc functionality.
Update on this topic: the ZFS snapshot sync that is implemented with the scripts I posted in February is running stable in test setups since 2 months. After some minor changes I will use this in production for hot and cold standby containers on ZFS storage volumes.