3 ms·

I guess there's a precedent there in the fact that unix file systems use reference counting for file links, presumably for the same reasons. Considering how wel

I guess there's a precedent there in the fact that unix file systems use reference counting for file links, presumably for the same reasons. Considering how well-architected tarsnap seems to be, I suspect you've taken steps to avoid losing data via inconsistencies in the reference counter?

cperciva 18y ago
... you've taken steps to avoid losing data via inconsistencies in the reference counter? There are some sanity checks built in, but in the extreme case what you're suggesting is impossible. Reference counts are managed on the client side, and the client has the keys necessary to delete blocks from the server; if the client is functioning correctly, it won't get the reference counts wrong, but if the client is malfunctioning then it could go berserk and delete blocks without even looking at the reference counts. I have taken care of the obvious issues, though -- as long as the OS implements fsync() properly, there's no way that tarsnap or the client system crashing will result in corruption.