Date: Fri, 29 Sep 2000 11:07:13 -0700 From: "Crist J . Clark" <cjclark@reflexnet.net> To: j mckitrick <jcm@freebsd-uk.eu.org> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: dump levels/incremental backups Message-ID: <20000929110713.A8019@149.211.6.64.reflexcom.com> In-Reply-To: <20000929140633.A63505@dogma.freebsd-uk.eu.org>; from jcm@freebsd-uk.eu.org on Fri, Sep 29, 2000 at 02:06:33PM %2B0100 References: <20000929033448.A59083@dogma.freebsd-uk.eu.org> <20000928200709.J81242@149.211.6.64.reflexcom.com> <20000929140633.A63505@dogma.freebsd-uk.eu.org>
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On Fri, Sep 29, 2000 at 02:06:33PM +0100, j mckitrick wrote:
[snip]
> | 3 2 5 4 7 6 9 8 9 9 ...
> |
> | For size concerns, notice that each dump contains no more than two
> | steps worth of changes. Now when we need to restore, say we have a
> | problem at,
> |
> | 3 2 5 4 7 6
> |
> | This point of the cycle. To restore the filesystem, we start with the
> | level 0, then 1, then 2, then 4, and then 6.
>
> OK, so level 0 is a mass backup. Level 1 is weekly, and the others are for
> each day of the week.
That is the recommendation of the example on the manpage. How backups
are done is a very strong function of one's own needs.
> When a failure occurs, you start with 0 then 1. For
> the rest, and tell me if there is a simpler way to explain it, you use every
> other dump that will end on the last good backup. Either
>
> 3 5 7 9 or 2 4 6 8 9
No. It just looks obvious to me, but now when I have to explain
it... You gotta think of how you are doing the dumps in reverse. If we
have,
3 2 5 4 7 6
And we need to now restore, there is no point in using the level 3
since everything that had changed since the level 1 (not shown) is
captured by the level 2 after it. There is no point in using the level
5 since the level 4 after catches any changes since the level 2, but
we need to keep the level 2 since it may have changes since the level
1 that a level 4 would have skipped. And so on...
There must be an easy way to express this as the inverted logic of how
a dump decides if a file is to be included, but I can't come up with
it right now.
> This might be a silly question, but since there are more numbers in the
> series than days in the week, does that mean you should just do a level 1
> and repeat the series when you reach 9 twice?
YMMV. Do whatever is convenient for you. If you want to save space, go
for the full cycle. If you want to be able to always do the level 1
Saturday morning, stop there in the cycle.
[snip]
> I have been experimenting with flexbackup, but it seems the tar output for
> some reason isn't browsable by m-commander. My goal is to have an automated
> backup system that allows me to easily browse the archives if need
> be.
I once (briefly) thought about making a catalogue of each backup as it
was made by doing something like,
# dump -$LEVEL -uaf - $FILESYSTEM | tee /dump/file/or/pipe | \
restore -tvf - > /dump/list/file
Then I got off the pipe.
--
Crist J. Clark cjclark@alum.mit.edu
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