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From: davidsen@steinmetz.UUCP (Davidsen)
Newsgroups: net.bugs.usg
Subject: Re: A good incremental backup for system V
Message-ID: <759@steinmetz.UUCP>
Date: Thu, 22-May-86 15:20:47 EDT
Article-I.D.: steinmet.759
Posted: Thu May 22 15:20:47 1986
Date-Received: Sat, 24-May-86 17:38:22 EDT
References: <151@ttrda.UUCP> <757@laidbak.UUCP>
Reply-To: davidsen@kbsvax.UUCP (Davidsen)
Organization: GE CRD, Schenectady, NY
Lines: 41


I am currently personally backing up three systems totaling about 200MB of
hard disk. This doesn't sound impressive, but I currently have to do it to
floppy disk! Honest, I think about backup *a lot*! I use backup/restore
(or dump/restore as it's called on some) whenever posible. I have had to
restore one system from cold twice due to hardware changes. Until cpio
will take care of deleting deleted files, I won't use it for regular
system backup. I run out of disk every time I try.

I have no ultimate answer, but I will offer one trick which has cut down
my hassles. Although I don't use cpio for system backup, I sometimes want
to backup a small directory for transfer to another system or for storage
before deleting the contents. The output of cpio may be piped through
compress (I have v4.0 from mod.sources) which reduces the volume of output
data to fit on one disk (usually). A friend uses this to backup a 75MB
system on a 40MB streaming tape. It eats CPU, but I don't have to sit and
change media, and he doesn't pay a third shift operator.

Second trick... if you have a large database which gets "changed" every
day, you may eliminate the backup by keeping one backup on disk and saving
an "incremental" of just that file. The program I wrote looks like a one
night stand between diff and cmp, but it works. You can backup the
database once a week (or whatever) and just take an incremental daily.
            ================ warning ================
This doesn't work on all databases, use your regular backup before you try
it. Some databases modify most of the file just to change a few records
(you can tell by response), while others are sensitive to the date changed
or something. I am ashamed of the code I use to do this so don't even ask.
If I ever clean it up I'll post it, after I have a lawyer read the
disclamer.

-- 
	-bill davidsen

  ihnp4!seismo!rochester!steinmetz!--\
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                    unirot ------------->---> crdos1!davidsen
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         sixhub ---------------------/        (davidsen@ge-crd.ARPA)

"Stupidity, like virtue, is its own reward"