indulis
I don't think jon is talking about some kind of "incremental" backup system because he is talking about backing up the database data not the actual media files themselves. Because media file's metadata is also stored in either an .id3 file or embedded id3 tag, there is no real call for backing up that part of the metadata - on complete reinstalls, all this metadata is automatically recovered by default and injected back into the fresh pluto_media database.
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Actually I was thinking about all of the other information associated with recordings in Mythtv (channel number recorded on, series ID, detailed program info etc). If we had this as a "data nugget" then in case of reinstalling a system I could move my episodes across to a new server.