[tahoe-dev] How many servers can fail?

Dirk Loss lists at dirk-loss.de
Sat Oct 29 07:11:49 UTC 2011


On 25.10.11 18:35, Nathan Eisenberg wrote:
> Of course, where it gets more complicated is the tree property of 
> tahoe-LAFS - which is to say that files are children of 'directories'
> which are distributed with the same erasure coding.  To visualize
> this simply, imagine that you have 1-of-2 encoding on a grid of 4
> servers (A,B,C,D).  The directory is stored on (A,B), and the file
> within it is stored on (C,D).  Should A and B fail, the file (which
> is NOT stored on A or B) becomes unavailable, even though C and D are
> online.

So files placed in a deeper directory structure have a higher risk of
getting lost, because every parent directory has to be available and
correct in order to find the files?

And since each of the parent directories might be placed on a different
set of servers, files may get lost because too many servers holding
information about their parent directories have failed -- although
enough servers might be available to reconstruct the files themselves?

Best regards
Dirk



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