SUMMARY: ufsdump level 0-9 ** 101

From: Rodolfo Levy (
Date: Fri Feb 20 1998 - 13:00:39 CST

Hi Everyone,

Thanks for the answers. I have included some of them in this summary.


Here is the original question,

> Can somebody explain me what's the difference between all the 9 dump
> levels.
> I'm setting up a backup schedule using ufsdump, but don't quite
> understand the ufsdump levels and how each level backs up data.
A level 0 dump gets everything.
A level 1 dump gets everything modified since the last level 0 dump.
A level 2 dump gets everything modified since the last level 1 dump.

I run weekly level 0 dumps and daily level 3 dumps. Since all my
daily dumps are the same level each one has all the data modified since
the last level 0 dump.
If I did a weekly level 0 and then a level 1 on Monday and a level 2
on Tuesday I would have to use all 3 tapes to do a restore.
Level 0 (Full Dumps) - Dumps that backup the entire file system

Level 1-9 (Incremental Dump) - Dumps that backup only those files that have
changed since the last lower level dump.

for a more detailed explanation please visit:

It's easy. Level 0 dumps the entire file system. All the other levels
dump only the files that have changed since the next lower level dump. The
dump levels are only numbered relative to each other; there's no absolute
measure of what each will dump. There are ten levels to give you some

For me, I do only two levels of backups. Periodically, I do a level 0 dump
of all file systems. Then, every day, I do level 5 dumps. The daily dumps
back up files that have changed since the level 0 dump. I could just have
easily used any other level number and obtained the same effect.

If I wanted to set up a more complex dumping schedule, I might do something
like schedule a level 1 dump on Sunday, then level 5 dumps on the weekdays.
The Sunday dump would copy all files that have changed since the level 0
and the weekday dumps would catch all files that have changed since the
level 1 dump.
backup level 0 backs up everything
backup level 1 backs up everything since the last level 0 dump
backup level 2 backs up everything since the last level 1 dump
backup level 9 backs up everything since the last level 8 dump

most people use 2 levels. some people follow the docs ('man ufsdump')
and produce nicely information-theoretic-optimised dumps using multiple
levels. your choice.

restoring: restore the latest level-0, then the latest level-1 since
that level 0, then the latest level-2 since that level-1, ... if it
turns out that there is no level-Y since the last level-X, for some
Y > X, skip that Y. E.g., if you have:
        0 3 2 5 4 7 6 9 8 9 9 ...
 1. ^
 2. ^
 3. ^
 4. ^
 5. ^
 6. ^

Backup levels:
0 = full backup
1 = incremental to previous level 0
2 = incremental to previous level 1
3 = incremental to previous level 2

Most people do a weekly level 0 and daily level 1.
This would mean only two sets of tapes are needed to
restore the complete filesystem, i.e. full and
incremental. Otherwise, you have to go through the
entire set.
Dump levels are very simple; level 0 means 'everything', and each
higher-numbered level means "anything changed since a lower-numbered
level dump was run". That means that running

        sat level 0
        sun level 1
        mon level 2
        tue level 3
        wed level 4
        thu level 5
        fri level 6

will give you the minimum amount of data on each tape (the level 0
will always have everything, of course), while running

        sat level 0
        sun level 5
        mon level 5
        tue level 5
        wed level 5
        thu level 5
        fri level 5

will give you more and more files on each successive tape (which makes
it easier to find a file for restoration unless it was deleted a few
days ago).

All of this came about when tapes were smaller than disks (even though
those disks were pretty small -- can you imagine running Solaris *and*
having user home space on a 300M disk today? ;-) and so you had to be
careful with your data and your juggling, but you didn't want to have
to search through *too* many tapes to restore something. In modern
terms, with tapes usually bigger than disk drives (though RAID happily
lets you get bigger than a 70G DLT), you can generally run a level 0
at your desired frequency and a level x, where x is constant, on the
other nights. I like using 0 and 5; should I have a need to fire off
a quick incremental "just in case" before doing something, I can use a
higher level to capture only things that changed since the last
incremental, and I could add a level 3 if my incremental tape were to
get too full (though the correct answer there is to change your backup
schedule or your tape size so that everything continues to fit).

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