Why not ZFS
ZFS is a hybrid filesystem and volume manager system that is quite popular recently but has some important and unexpected problems.
It has many good features, which are probably why it is used: snapshots (with send/receive suppport), checksumming, RAID of some kind (with scrubbing support), deduplication, compression, and encryption.
But ZFS also has a lot of downsides. It is not the only way to achieve those features on Linux, and there are better alternatives.
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