Trashed MFD on PDP-10 in 1970 (Score 1)

1970, freshman computer science student, large PDP-10 system which supported the entire university computing. Working on a program which could find deleted files again by picking up the traces still on the disk. If the newly freed blocks hadn't been overwritten yet, that is... Testing the program, accidently wiped out the MFD, Master File Directory. (Man, it's been a lot of years since the though "MFD" went thru my head! Ah, the fond memories!) All files, many hundreds of students, several commercial operations, all gone in an instant! Entire system gone! RAN for the big red button. And yes, it actually was a big red button! Rebooted with no users, spent about 24 hours running the program. It took that long, it read each disk block sequentially with no buffering, wrote found files to tape, then restored from tape when all was done (so as not to wipe out files as it found files)! And I got all the files back!! Administration not too happy, but at least I proved the worth of my program!