Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!ucsd!network.ucsd.edu!celit!hutch From: hutch@fps.com (Jim Hutchison) Newsgroups: comp.unix.large Subject: Re: Epoch like filesystem Message-ID: <11709@celit.fps.com> Date: 17 Oct 90 07:56:57 GMT References: <60058@bbn.BBN.COM> Sender: daemon@fps.com Reply-To: hutch@fps.com (Jim Hutchison) Organization: FPS Computing Lines: 31 In article <60058@bbn.BBN.COM> chowe@bbn.com (Carl Howe) writes: >rodney@sun.ipl.rpi.edu (Rodney Peck II) writes: >>[...deleted...] >>Why not write some code to make a standard sunos system behave like Epoch? >>[...deleted...] >Plan 9 from Bell Labs does a similar sort of thing. They back up the >entire contents of their hard disk to optical every night as part of >the standard file system tree. For example, all files created or changed >today would end up in the file system under /1990/1015/... Yesterday's >files would be under /1990/1014/.... The hard disk on any given day >only contains the changes since the last optical backup. You end up >with both fast access to recently created data and on-line access >to all backups. O.k. I'll bite, how does such a system last? At the end of each month does it make a "level 0 dump" file system? Certainly at some point the on-line optical disk resources will be exhausted and some sort of consolidation will be needed, or the system will have to grow continuously at a rate determined by day-to-day disk activity. It seems that consolidation could limit this growth, and allow for old "level 0 dump" disks to be migrated onto a shelf or into a safe place. With the current speeds for optical drives, I'd kind of guess this system is not useful as a primary storage device. Presuming WORM and not M-O, it couldn't be used for frequent migration, due to the rapid rate at which the platters would fill up with minor revisions. -- - Jim Hutchison {dcdwest,ucbvax}!ucsd!fps!hutch Disclaimer: I am not an official spokesman for FPS computing