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Tue, 25 Mar 2008

POHMELFS status.

I've started mostly from scratch, I think it is a good sign, when project can be rewritten without any pain to implement a really interesting ideas instead of having multiple crutches all over the place. This also means that it is not that complex, so I do not regret about dropped code.

Now it is in a very testing stage without network protocol at all, but I test new paradigm in the pohmelfs: its inodes will not be hashed into global hash table, but instead will be placed into local trie-like structure, which (optionally) will allow RCU-fied lookup. Something similar to data structure created for multidimensional trie used for unified socket lookup patch.

I very like two-hash approach, but since there is no proof (yet) it will work for all possible cases, I will first implement radix-like tree to store object names. Network protocol will also operate on full-length pathes, which actually can be a bad idea, I will see.

Another uber cool feature of the full-path approach is ability to create number of directories, which form a path to given object, in a single command, i.e. when client sends a network command to create object /a/b/c/d/file, there is no need to send separate commands to create /a, /a/b and so on, it can be done automatically by server. This requires to send not only path though, but also information about permissions for each subdir.

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