I'm moving terabytes of my archives to new disks and noticed that kdiff3, which I have been using to verify copied folders, is choking when giving multigigabyte 7z'ed files to verify. Biggest memory used by kdiff3 in Activity Monitor was 49GB... So, I looked other choises and found old "File Compare 1.1" by Softhing. Would be nice to be able to choose 3 files to compare (since I'm always making 2 backups), but I'm thinking about how reliable this app is? It calculates md5 of a multigigabyte file, which is in a NAS with 1Gb connection, in a few seconds! Are these md5's precalculated in filesystem? Would it be more sure to re-calculate?