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Path: utzoo!utgpu!water!watmath!onfcanim!dave
From: dave@onfcanim.UUCP
Newsgroups: comp.cog-eng,comp.unix.xenix,comp.unix.wizards
Subject: Re: Request for human interface design anecdotes
Message-ID: <15478@onfcanim.UUCP>
Date: Sat, 21-Nov-87 19:09:34 EST
Article-I.D.: onfcanim.15478
Posted: Sat Nov 21 19:09:34 1987
Date-Received: Mon, 23-Nov-87 00:36:13 EST
References: <101@ateng.UUCP> <1402@cuuxb.ATT.COM> <1689@rayssd.RAY.COM> <3032@phri.UUCP>
Reply-To: dave@onfcanim.UUCP (Dave Martindale)
Organization: National Film Board / Office national du film, Montreal
Lines: 36
Xref: utgpu comp.cog-eng:298 comp.unix.xenix:1036 comp.unix.wizards:5151

In article <3032@phri.UUCP> roy@phri.UUCP (Roy Smith) writes:
>
>In fact, I have given serious thought to running incremental
>disk-to-disk dumps several times a day here to narrow the window of
>vulnerability from a whole day to a few hours.  Yes, I know dumps on live
>file systems don't always work, but it's better than not doing it at all.

There is an even better way.

We run a "backup daemon", originally written by Ciaran o'Donnell at Waterloo,
and still in use there, which is called from the crontab (every hour in
our case) to scan a list of filesystems looking for files that were
changed since it was last run.  When it finds one, and it isn't too large
and its name doesn't pattern-match a list of "not worthwhile" names like
"*.out", it copies it into a backup fileystem.

If the original filename was /u/dave/film.c, the copy will be named
/backup/u/dave/film.c/Nov20-19:01.  If I change the file again, it will
be backed up again an hour later, with a filename that reflects the changed
time or date.  Then, when I trash a file through carelessness, I have
a whole "history" of backup copies to go back through, so even if I introduced
a bug 5 hours ago, I can generally get back the code before that.
And I don't have to run "restore" to look for it; I just chdir to
/backup/u/dave/film.c and look around.

The /backup filesystem must be dedicated to the use of the backup program,
since it keeps it from filling up by deleting the oldest files as necessary
to make room for the new ones.  We use a 30-Mb partition, which seems to
keep stuff around for about a month on a system with 4 people writing code.

The only way I still lose files is if I clobber them within the first hour
of working on them (often it's withing the first 2 seconds when it happens!)
and the file hadn't been touched for 2 months before that, so all old
copies have been deleted.  So then I have to get out the tapes.
But it works most of the time, gives me a backup every hour of a file that
I am changing frequently, and requires no work on my part at all.