On 03/26/13 12:37, Philipp Riegger wrote: > I am thinking about using one tarsnap key for multiple systems to > improve the effectiveness of the deduplication. There are multiple > possibilities how I could approach that: > > 1) Share the cache between the systems. I'd probably have to make sure > that no 2 backups are running at the same time and that no 2 instances > of tarsnap are using the cache at the same time, is this correct?
Correct. Tarsnap won't let you create two archives at once, in fact -- if you try then one of them will error out. > 2) Keep a seperate cache on every system. A very naive approach would be > to run fsck before every backup. But that takes a lot of time and wastes > some bandwidth, I think. Running fsck before every backup would dramatically increase your bandwidth costs. Not recommended. > Is this kind of setup recommended? What is the best way to implement it? Given your suggestion of sharing the cache, am I right in thinking that you're backing up multiple systems which are close together (geographically or networking-wise)? Can you have one system which runs Tarsnap and reads data from the others (via NFS / SMB / etc)? > Would a tarsnap command line option be possible, that does what I need > from the fsck, just faster and using less traffic? Hmm... theoretically writes could be done with a "mini-fsck", but you'd need to do a full fsck before you could delete any archives. Still, this is an interesting possibility... I'll have to think about this. -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
