Share a key between multiple systems

[Philipp Riegger <lists@anderedomain.de>]

Hi,

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?

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.

Is this kind of setup recommended? What is the best way to implement it?
Would a tarsnap command line option be possible, that does what I need
from the fsck, just faster and using less traffic?

Thanks
    Philipp