I studied working of ZFS while LXD container migration. From the article
https://pthree.org/2012/12/14/zfs-administration-part-ix-copy-on-write/, summarized that LXD by default uses directory (dir) backend storage mechanism, which slows down the system and creates performance overhead because it copies whole container’s file system every time. So, ZFS storage system which uses a copy-on-write (COW) mechanism to record only the changes that occur after the snapshot and transfer modified contents only rather than the entire container’s file system. Therefore, ZFS is preferable for container migration.
Please add your valuable point for the role of ZFS in container migration.