[Borgbackup] Lots of files that change rarely and predictably

[Thomas Waldmann]

> I think I was unclear. The recent mail folders and files are practically
> the only ones that ever change, so I want to tell borg to assume that a
> file has stayed the same if it is outside of the recent mail directory.

I understood that, but it would be somehow weird (or at least "very
special") for a backup tool to rely on that without even looking.

You have to keep in mind that borg always does full backups, so the
backup that works your way would include directory contents borg did not
even look at. Besides that, there is a slight additional problem that
borg always reads xattrs/acls from the fs as they are not contained in
the files cache.

> I arrived on an approach of making two types of archives, one with all
> 670,683 files, (Call this the "full" backup.) and another with just the
> 6,765. (Call this the "recent" backup.) I would usually run the recent
> backup, and I would run the full backup only when I changed files in
> other directories. When I restore backups, I first extract the newest
> full backup, and then I extract the newest recent backup on top of that.

Yeah, guess that would work.

>   $ time borg create --compression lzma,9 \

Don't use lzma levels > 6 with borg, it is just a waste of cpu cycles
and won't improve compression due to borg's chunk size.

> I was using MicroSDHC with ext2 filesystem as the storage medium when
> I originally inquired about this style of backup, and so I may have at
> the time had the slowest possible email storage stack.

I've bad experiences with SD card reliability. Would never use them for
backups. Also performance is usually less than great.

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