Epoch like filesystem

[Jim Hutchison]

In article <60058 at bbn.BBN.COM> chowe at bbn.com (Carl Howe) writes:
>rodney at 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.
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Jim Hutchison		{dcdwest,ucbvax}!ucsd!fps!hutch
Disclaimer:  I am not an official spokesman for FPS computing