On Tue, Aug 13, 2002 at 03:18:30PM -0700, Charlie Bebber wrote:
> Good afternoon,
>
> This being the first time I've been responsible for doing backups, I'm a
> bit lost and sure could use some enlightening with regard to run and
> dump cycles and general rules of thumb. Basically, I'm a backup newbie.
>
> We've got an external Compaq eight cassette 20/40Gb DAT autoloader
> hanging off of one of our linux boxes with seven tapes and one cleaner.
> There are 10 other machines (linux and Solaris) that will have to have
> various filesystems backed up, but I need to figure out how often to
> back up and what's the best way to cycle the tapes and whatnot.
>
> Is the general rule of thumb to use one tape for a respective day -- one
> that gets used repeatedly on Mondays, another for Tuesdays, etc.? And
> when the tape comes back into use, does the previous data get
> overwritten or is it appended to the previous dump? Like I said, I'm
> pretty much a complete newbie with respect to backups, so I apologise if
> these are "dumb questions" that any schmuck should know. But I'd sure
> appreciate any suggestions and recommendations.
Do not consider the following discussion of amanda to be typical of
backup software. Amanda does have some unique aspects.
Tapes are not assigned to specific days, types of backups, or whatever.
Each is labeled uniquely and for human consumption the uniqueness comes
from sequentially numbering them. But they could just as well be labeled
Huey, Dewey, and Louie.
Once in use they will probably be used in the same order each time.
Amanda never adds a second dump session to a tape. Each use overwrites
what was on the tape previously.
You have 11 machines, the tape server and 10 clients. Say on average each
has 4 file systems. You would then have 44 items (host/filesystem) to backup.
These would each be listed in a file called "disklist".
Backups, called dumps regardless of the backup program (dump or tar) are
performed at "levels". A full dump (everything on a disklist entry) is a
level 0 (zero). Others levels are known as incrementals, level 1 means
everything changed since the last level 0. Level 2 dumps are everything
changed since the last level 1.
Traditional backup strategy says do all level 0's on the same day taking
a huge amount of tape and time. Then on other days do incrementals running
much faster and using a small amount of tape. Amanda changes this by
mixing on each day, level 0's of some disklist entries, incrementals of
others. The aim is to use the same amount of tape and time each day.
You will have to decide your "dumpcycle", how long amanda is allowed to
go between level 0's. I use 1 week, but if my data were more critical
I might consider reducing that. As it is, my data is not super-critical
and if need be I'd bump it up to make everything fit on one tape.
Next you will need to decided how often you will run amanda dumps (amdump
program). Many sites run amdump every day. I only do it 6 days a week
because my tape changer holds 6 tapes (I clean manually as needed so all
slots hold backup tapes). This is specified as runspercycle (dumpcycle)
so my 1 week dumpcycle gets 6 runs of amdump.
You must also decide how many tapes you are willing to devote to your
backup scheme. Don't be stingy. Particularly as you are using relatively
inexpensive tapes. I keep 24 tapes in rotation. Since they are used
6 per dumpcycle (1 week) I have 4 weeks worth of dumps available. I picked
that number because my drive uses cartridges holding 6 tapes each and I
had 5 cartridges. Leaving 1 for general use, 4 were available for amanda.
Now over each weekend I just swap cartridges. The number of tapes in
service is specified as tapecycle.
All this info is collected in a file called amanda.conf.
With this as a starting point, get the source code, and in a directory
called docs are many information documents. An important one is INSTALLATION.
Also see the example amanda.conf file for all its comment remarks.
Hope amanda treats you well.
jon
--
Jon H. LaBadie jon AT jgcomp DOT com
JG Computing
4455 Province Line Road (609) 252-0159
Princeton, NJ 08540-4322 (609) 683-7220 (fax)
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