Which do you prefer and why for HDD or SDD hard disks ? And how is Ext4 with power failures nowadays ? iirc a few years ago there were issues with Ext3 (Yes, Ext3) and I remember a no barrier option was needed ? Is Ext4 much better ? And what FS do you prefer on usb storage ?
Maybe the example I gave was not enough.
The point of snapshots is serving as some kind of incremental backups always dependent of a main backup or the main instance.
Always the changes are copied, it is valid, even if a delta of a file was the only thing saved.
This applies to systems with deduplication enabled and COW.