On Thu, Oct 25, 2012 at 10:50 PM, hi <hi@guanyu.name> wrote:
where is meta data store in tahoe, is it stored on the tahoe client server?
Hi. In typical Distributed File Systems like gluster, the contents of the files are distributed across many storage servers, and the "metadata" is managed by a single metadata server or a small cluster of metadata servers. By "metadata", Distributed File Systems folks mean the directory structure -- what files are under what paths -- and ownership and permission bits and timestamps, and also maybe some information about which storage servers are holding which files. In Tahoe-LAFS, the directory structure part of that is encrypted by the storage client and then uploaded to the same storage servers that hold the file data. Those storage servers can't tell whether a given block of ciphertext that they've been asked to hold contains encrypted file data or encrypted directory data. In Tahoe-LAFS, the "which storage server holds which file" question is answered by the client *searching* the servers for the file when it wants to read or write it. This means no metadata anywhere needs to be updated when storage servers come and go, but it does mean more network operations are needed to begin uploading or downloading a file. We use a consistent hashing scheme, with a "tweakable" extension invented by Brian Warner, to make it so that the client usually looks in the right place to find the file with its first guess. Regards, Zooko _______________________________________________ tahoe-dev mailing list tahoe-dev@tahoe-lafs.org https://tahoe-lafs.org/cgi-bin/mailman/listinfo/tahoe-dev ----- End forwarded message ----- -- Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE