Aucbvax.2413
fa.works
utzoo!duke!decvax!ucbvax!works
Thu Jul 23 01:56:33 1981
File Backup
>From Joe.Newcomer@CMU-10A Wed Jul 22 23:56:57 1981
The Spice project plans to treat the local disk as a cache for
the central file system. Thus, primary backup is handled by
the same staff which backs up all our other systems. Local
disks will not have substantive amounts of private data which
is not replicated on the CFS.
In the case of workstations not on a network, if we abandon
such archaic ideas as single-task workstations, files without
timestamps, and similar absurdities, and produce some reasonably
intelligent software, a background task which does hourly, daily,
or as-needed backup to a floppy disk or other medium such as
streaming tape, occasionally prompting the use to insert a new
disk or tape, and which handles the grubby details of how to do
file retrieval in case a file restoration is necessary seems the
obvious simple solution. As I am currently thinking about having
a personal 68000-based system at home, which will not be on a net-
work, and cannot use CMU's machines for backup, this is one of the
first pieces of software I would build. My plans are to simply
assign ascending serial numbers to the floppies, and keep a file
(which is naturally backed up) which is a migration archive file
[CMU-10A users will recognize this as MIGRAT.DIR...]. Since all
REAL computers (not toy computers, no matter how powerful) have
date-time stamps which can go on files, the software architecture
is reasonably obvious.
Those ridiculous systems in which one can save or restore the
entire disk, but not do incremental save or restore, are not
worth talking about. I certainly don't want to reset my
entire disk to yesterday afternoon just because the system or
I accidently damaged one file.
More sophisticated applications, including large databases, need
more sophisticated incremental backup procedures. But these are
ALL OBVIOUS and can be ALL AUTOMATED. Using "clerical people"
or "professional people" means we've forgotten the best drudge of
history: the computer itself. The overhead on anyone to write a
serial number on an existing disk or streaming tape and insert a
fresh one is so small as to be unnoticeable. (Of course, I would
never consider the problem of "tying up the floppy drive" while
doing backup; floppies are not reasonable as secondary storage for
serious applications; they are far too small and slow compared to
even the current processors they are mated with. I consider a 10Mb
disk as small, but marginally acceptable, on a personal workstation.
24Mb is acceptable, 100Mb is reasonable. Floppies are at best a
cheap backup medium, not to be used for serious storage. I have
a small personal database which already exceeds 1Mb).
joe
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