Re: Tarsnap de-dup - one machine or all?

[Graham Percival <gperciva@tarsnap.com>]

Hi Arthur,

Deduplication is tied to each machine key.

If you have multiple machines using the same key, then data will
be deduplicated between all those systems [1].  If you have
multiple machine keys, then there will be no deduplication between
them.

[1] If you are sharing a machine key, then the cache dir should be
kept in sync between those machines:
http://www.tarsnap.com/multiple-machines.html

If you're just "moving" from one system to another, then you don't
need to worry about keeping the cache in sync.  Just copy the key
and cachedir over, then test it with --dry-run and you should only
see a tiny amount of new data (metadata).

Cheers,
- Graham


On Thu, Sep 17, 2020 at 08:50:13AM +0100, Arthur Chance wrote:
> Does tarsnap's de-dup work on one machine at a time or across all
> machines in an account?
> 
> The reason I ask is because I've moved a largish mail archive from one
> machine to another and am unsure whether the backup on the new machine
> will reuse the blocks from the old one, or whether I'll end up using
> double the space.
> 
> -- 
> The number of people predicting the demise of Moore's Law doubles
> every 18 months.