Re: Pre-flight check....

[Nick Sivo <nick@ycombinator.com>]

I've found tarsnap to be most effective for multiple point-in-time
backups of uncompressed, mostly unchanging data. Any file type is
supported, but alternate file streams or other unique filesystem
specific features may not be supported. If you don't know if you're
using these, then you're not :)

Uncompressed because tarsnap does compression just fine, and
compression of all your data usually achieves a better ratio than
compressing individual files.

Mostly unchanging because tarsnap is smart enough to re-use blocks
it's seen before - I keep 4 backups per day of around 40GB, but each
archive is only an additional 200-400MB (before compression) because
most of the data is unchanged:

root@znews:~ # tarsnap --keyfile ... --print-stats

                                       Total size  Compressed size
All archives                               1.3 TB           310 GB
  (unique data)                            395 GB            31 GB

So despite being able to restore any of the 80 backups in the 1.3TB
set I'm only paying to store 31GB. Win.

-Nick

On Fri, Feb 14, 2014 at 9:22 AM, John Gamble <jg5@sanger.ac.uk> wrote:
> Hi,
>
> I'm about to try out Tarsnap for the first time this weekend, but before
> doing do, wanted to check on a couple of things.
>
> 1).  Is Tarsnap suitable for _all_ file types, or are there any types of
> files that it has problems with?  I'm intending to back up quite a different
> variety of file types - text, photographs, music, and so on, and thought it
> might be better to ask this question first.
>
> 2).  Does the archiving process ( i.e. use of the 'tar' command) alter the
> original files in any way?  Again, I'm pretty sure it doesn't, but thought
> it better to be safe than sorry.  I was concerned that if, for some reason,
> I couldn't get the archiving to work, it might damage the original files.
>
> Thanks for any advice on these matters.
>
> Regards,
>
> John Gamble
>
>
>
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