The long road to recover Frogger 2 source from tape drives
This is just random, but reading this and the backup discussion made me think about SGI IRIX and how it could do incremental backups.One option was to specify a set of files, and that spec could just be a directory.  Once done, the system built a mini filesystem and would write that to tape.XFS was the filesystem in use at the time I was doing systems level archival.On restores, each tape, each record was a complete filesystem.One could do it in place and literally see the whole filesystem build up and change as each record was added.  Or, restore to an empty directory and you get whatever was in that record.That decision was not as information dense as others could be, but it was nice and as easy as it was robust.What our team did to back up some data managed engineering software was perform a full system backup every week, maybe two.  Then incrementals every day, written twice to the tape.Over time, full backups were made and sent off site.  One made on a fresh tape, another made on a tape that needed to be cycled out of the system before it aged out.  New, fresh tapes entered the cycle every time one aged out.Restores were done to temp storage and rather than try and get a specific file, it was almost always easier to just restore the whole filesystem and then copy the desired file from there into its home location.  The incrementals were not huge usually.  Once in a while they got really big due to some maintenance type operation touching a ton of files.The nifty thing was no real need for a catalog.  All one needed was the date to know which tapes were needed.Given the date, grab the tapes, run a script and go get coffee and then talk to the user needing data recovery to better understand what might be needed.  Most of the time the tapes were read and the partial filesystem was sitting there ready to go right about the time those processes completed.Having each archive, even if it were a single file, contain a filesystem data set was really easy to use and manage.  Loved it.