On Sun, Mar 31, 2013 at 6:18 AM, Stefano Mori <[email protected]> wrote:
>
> On 30 Mar 2013, at 18:23, Arno Hautala <[email protected]> wrote:
>
> I wondered about the hard linked directories, but couldn't imagine how that 
> got past the need to unlink thousands of files. Is there some interesting 
> algorithm in there?

By hard linking a directory, there isn't a need to link any of the
files contained in that directory. Think about your Applications
folder, which probably isn't changing every day or even week, let
alone every hour. TM can hard link /Applications and that one link
essentially covers all of the files and folders within it. When
pruning that backup it also just needs to delete one link instead of
visiting every file and folder.

Hand linking directories can be dangerous though (what if you make
A/B/C -> A), so it's a feature that isn't exposed to user tools.

>> Now I just rsync directly to the backup
>> location (running on FreeNAS) and rely on ZFS snapshots to quickly
>> make and prune old backups.
>
> Oh, cool.
>
> Should I look at MacZFS?

If you're not working with a lot of data? Probably. ZFS is notorious
for being RAM hungry. I think the recommendation is no fewer than 4 GB
(not entirely unreasonable these days I guess), but you very quickly
will want more. At a stretch you can probably get away with 1GB per
TB, but I'm pretty sure that wouldn't be a great experience.

If you have a spare drive to play with, why not? I think Zevo is the
most current ZFS version, though the free version does have some
potentially annoying restrictions (it's probably fine for new users
and playing around).

--
arno  s  hautala    /-|   [email protected]

pgp b2c9d448
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