> To foster my understanding, I've tried to visualize what that means: > > http://dirk-loss.de/tahoe-lafs_nhk-defaults.png > > Is that interpretation correct? > > Best regards > Dirk To great extent, yes, although operating with 7 servers in a 3 of 10 encoding is suboptimal. To keep things simple, you might simply set H=N (10), so that uploads will fail if they cannot be evenly distributed among 10 servers.
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. I've mentioned previously on the list that this seems to be a design issue, and that perhaps dircaps should be a special type of share that is always distributed (and redistributed) among all tahoe servers regardless of N or K or H. However, I will readily admit that this is probably easier said than done. Nathan Eisenberg _______________________________________________ tahoe-dev mailing list [email protected] http://tahoe-lafs.org/cgi-bin/mailman/listinfo/tahoe-dev
