From my understanding, deduplication takes place on the host, not theOn Wed 05 Sep 2012 03:33:59 PM EDT, David Prager Branner wrote:
> I'm new to Tarsnap as of last night and am very pleased with it. I
> have this question:
>
> I have some duplicate files on different machines, both backed up to
> the same Tarsnap account. It appears to me that in this situation, the
> usual economizing of space and archiving time — as when identical
> content is placed in the different archives on the *same* machine — is
> not taking place. Is that correct? Or is there something I can do to
> effect a savings here?
>
> Many thanks!
server thus the data being backed up from two different hosts would not
be deduped against each other. Additionally, since all data is
encrypted in such a way that only the client is able to decrypt it, the
same raw data being backed up by two different hosts would be different
on the server (provided that you use different keys for each host, as
you should from a security standpoint).
If you wanted to deduplicate backups from multiple hosts against each
other, you would need to copy the backups to a unified location, then
do one unified tarsnap backup of all the data from that centralized
location. This shouldn't be hard to do using rsync (provided your
machines are in the same physical location or at least have a decent
amount of bandwidth between them).
Of course, this is all written based on my limited knowledge of the
internal workings of tarsnap, so I could be wrong. If so, someone feel
free to correct me :)