I believe that since some decision must be made *when* a snapshot is taken,
and that should (has to) be done by userspace, a userspace versioning system
for doing the backups is the right solution. [1]
Whether there is some filesystem (FUSE or native) that allows online browsing
of the backups or not is another matter.
Ad 1: What userspace needs is
- atomic snapshots of complete directory trees, independent of mount
boundaries (across filesystems)
- an atomic way to change the state of the filesystem for the *whole* system.
For FSVS I'll try to use unionfs for that - populate some new directory with
my tree of changes, then overmount that over "/", and move the files over
one-by-one until the new directory is empty. (Must be checked on reboot, of
course).
These are actually two similar operations (from the atomic view), but have to
be done in completely different ways ... Maybe there could be some "better"
interface (if there is one - I don't know what could really be removed from
the above workflow).
Regards,
Phil
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