Re: [Tails-dev] An outside of the box proposal re persistenc…

Hi alienpup,

alienpup (2021-08-02):
> The now rather lengthy (lengthy is good) discussion regarding Tails
> persistence backup has not considered the benefits of an alternative
> persistence file system, one designed with fast, easy backups in
> mind. Of the several such file systems that come to mind, btrfs is
> perhaps the easiest to implement. […]
>
> If the Tails persistence volume were a btrfs file system, any backup
> application could be employed to copy data there. The btrfs
> "snapshot" feature would then make what are in effect incremental
> backups simple and fast. These snapshots require very little
> additional storage space, and rather than being something special to
> the btrfs file system, snapshots are basically subvolumes which can
> be browsed and/or mounted. Importantly, any backup application
> running on any other Linux file system can move data into and out of
> a btrfs file system. No walls, no fences, and no special backup file
> formats required (though optional).

The way I understand your suggestion:

- This would not, in itself, solve the problem we focused on so far,
that is having backups in the first place (S1 on the blueprint): we
still need $something to copy data to that (btrfs) filesystem on
another storage device.

- Instead, this could be an optional follow-up step to implementing
backups via the "Clone Persistence in Tails Installer" solution
we've picked so far. It would solve S4 via incremental backups.

- The implementation draft we have on the blueprint for the "Clone
Persistence in Tails Installer" solution, based on rsync, is
entirely compatible with your suggestion. It does not prevent us
from switching to a different filesystem for Persistent Storage
later, and taking btrfs snapshots before/after updating the backups,
if/when we identify S4 as a priority.

Correct?