We haven’t seen any corruption caused by the migration. We need the corrupted log file and the hashtbl to have a look, but I see higher chance for real disk corruption.
The only known risk is that we don’t use fsync for performance reason. The last few pieces in a log file can be zero if OS doesn’t write them out from the cache before a ungraceful shutdown (which supposed to be rare).
Jeff is working on an automatic fsck to make to avoid these problems. Next release will generate some “hint” files for each hashtable. Including the log files which should be checked (instead of checking all of them).
Piece-hash is included in the pieces headers, so technically it’s possible. We don’t have tool, and it really depends the corruption type. If only one or two pieces are affected, it might be easier to just keep the log file as is.