Copied before every start of the machine, and kept several deep rather than
copied over one file.
ONE BACKUP TAKEN AT EVERY START IS WORSE THAN NONE. The way a disk is lost is
that something goes wrong - and the very next thing anybody does is start the
machine again to see how bad it is, which is exactly when a single backup gets
overwritten by the wreckage. Three deep means the damage has to happen and then
be started past three times before the copy that would have helped is gone.
AND IT IS NOT GUARDED BY A CHECK THAT THE DISK STILL LOOKS RIGHT, because no
such check can be written. The disk that went missing this week was a perfectly
valid and perfectly empty filesystem: the format had succeeded, and there is
nothing to look at that says a disk has lost anything. That is the whole reason
to keep the old ones rather than to judge the new one.
The backups sit outside clean's reach like the disk itself. A backup a rebuild
deletes is not one.
The message the disk prints when it is first made said "nothing in this makefile
will touch it again", which stopped being true the moment this was added. It now
says written to, and says where the copies go.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
AnachronautandClaude Opus 5
925388c2f2