On Thursday 28 November 2002 19:22, Joffer wrote:
>I just got 7 tapes and an old scsi tape streamer from a friend. I
> will be installing Amanda and was thinking I would use the
> following backup scheme.
>
>The 7 tapes are "devided" into:
>2 Tapes OFF-Site
>4 tapes = 4 weeks , mon-sat = incred, sun = full dump
>1 - backup tape just in case
>
>The backup-scheme would be like this.
>
>First I run a full backup using the 1st of 2 OFF-SIte tapes. I
> think I should create a second config for manuel archiving,
> wouldn't that be the best solution?
>
>Then, I'd let the backupcycle begin:
>1st of 4 Cycle tapes: Midnight each Monday to saturday -
>changed/new files only Midnight Sunday - Full backup -
>Eject backup - insert 2nd of 4 Cycle tapes
>
>2nd of 4 Cycle tapes: same schedule as 1st tape of course.
>
>3... same as 2nd etc
>4.... etc
>1..... etc
>2...... etc
>
>and when my schedule or my instincts tell me it's time for a new
> full off-site backup I do a manual full backup on 2nd of 2
> OFF-Site tapes while my normal cycle goes as normal (if I
> remember to insert the cycle tape again after I've done a manual
> one :)
>
>Since I've never used a tape streamer before and not very much
> into the backup-scheme, I'm asking for comments on my
> backup-scheme. I'de also very much like to get input on how to
> achieve this.. can't say I understand the runspercycle and
> typecycles etc just yet..
Hoo boy, here we go again, somebody wants to mold amanda to their
way of thinking. :-)
Note the smiley please as you read on.
I think your last paragraph is maybe the most accurate.
You're going to have 4 problems I'd suspect.
1. That drive isn't big enough to backup anything much more complex
than a floppy based firewall. You've got 90 meter tapes which will
hold 1 gig (uncompressed) on a really really good day. How big did
you say your hard drive was?
2. That drive, if it has any real use on it, probably has a
headwheel thats on its last legs, with an accompanying high error
rate. I hate to toss water on your fire, but those drives go for
less than a 5 dollar bill on ebay when they do sell, and I suspect
many of them cost the seller the sales fee and still go unsold.
With proper use of the cleaning tape, it may go for 2500-3000
running hours, and that can pile up in a couple of years if its
been doing anything like a daily backup of what must have been a
pretty small system. ISTR its data rate isn't more than 200kb a
second, pretty slow in todays world.
3. You want to bend amanda to run things your way, and thats quite
difficult for a newbie. Amanda's philosophy is to take what you
give her, and do the maximum she can with it. That means amanda
will want to be run every night, but its amanda who will decide the
scheduleing, and amanda attempts to spread the backups out and
adjust things on a day to day basis that will in time result in
each nightly backup using about the same average amount of tape.
To that end you have 4 variables to control the outsides of the
envelope amanda can use.
1st is the tapetype defined size of the tape, in your case maybe 950
megs uncompressed. Turning any hardware compression the drive has
off is the general recommendation because with it on, amanda can't
get a clear view of how big the drive is and you have to fudge that
value, sometimes a lot depending on the compressability of the data
you backup, an unknown. Besides, a software compressor can usually
do a better job, sometimes by amazing ratios. Amanda will develop
a history of how each disklist entry compresses, and can after a
few runs, have a very good idea of how much raw data she can put
thru the compressor (usually gzip) and still make it fit the tape.
2nd is the 'dumpcycle' in amanda.conf. This defines to amanda how
many realtime days she has to fit all the stuff you want backed up
into the schedule.
3rd is the 'runspercycle' in amanda.conf. This tells amanda how
many runs she actually has in the time defined by dumpcycle to do
her job.
4th is the 'tapecycle' defined in amanda.conf. This tells amanda
how many tapes she has to use, and indirectly how quick she can
re-use a given tape.
Now, to give you an idea, and I'm just a 2 machine home network guy
who doesn't backup the second machine directly, but maintains on
this machine, a set of rsync'd 'important' directorys that are
backed up.
Thats a total of about 150 gigs worth of drives, none of which is
even remotely close to half full after my last re-arrangement.
My drive is a changer, a 4 tape changer that I leave a cleaning tape
in the bottom of the magazine, so it has 3 tapes available, which
are DDS2's at nominally 3.85 gigs per tape uncompressed. I
practically stole it on ebay about a year ago, 135 USD, brand new.
I'm currently waiting for the schedule to settle a bit, having
reduced dumpcycle and runspercycle from 7 days to 5 days over the
last week. And I've added a few more tapes to the rotation so
there are now 28 tapes in the 'tapecycle'. It shelved a full in
favor of an incremental last night because the tape would have hit
EOT and I haven't given it permission to 'runtapes' more than 1.
So in that 5 nights running, I have the ability to fully backup
5x3.9 or about 17.5 gigs in that 5 days.
With your tape stock, .95 gig x 7 tapes=6.65 gigs if all were used
in the dumpcycle. However, this is not a very good arrangment
because with every tape change, you will be overwriting the last
good fulls of something or other. This is why I have what to you
looks like way too many tapes, but if the 5,5,28 schedule actually
works, I will have 5.3 full level 0 copies of everything here. If
not, then I go back to 6 and 6, giving me 4.4 copies of everything
on the shelf, actually a smallish solid oak pigeonhole rack I made
in the shop. We have lots of oak trees here in WV, USA. :-)
You need at least 2 full copies so that if one fails, you haven't
destroyed your only good, but slightly older backup of that
partition. This is what backing up is supposed to do, give you
nearly bulletproof recovery.
Also, be aware that amanda cannot, and possibly never will, have the
ability to append to an already written tape, again the idea is
bulletproof data security. No one knows who might eject a tape
during the day and reinsert it, thereby rewinding it and destroying
the location knowledge of where it is on the tape. When that
happens, then the next nights incremental goes on the headend of
the tape and everything beyond it on the tape from previous writes
is then beyond recovery. Amanda rewinds the tape before she
starts, and reads the tape ident label you put on the tape, and if
its not due in the tapecycle, then amanda won't use it.
However, if you have holding disk space enough, you can leave the
drive empty for several days and then 'amflush' whats there to one
tape provided it will fit. When using a holding disk area, be sure
and leave it out of the disklist, or exclude it in amanda.conf, no
use backing up what you've already backed up.
Amanda can stand guard over your data like a vicious dog, but she
would much rather she was allowed to do it her way. If thats not
to your liking, then you should probably investigate other
software, it would be easier for you in the long view. I also
don't think the other software and methods will be as dependable
but that one mans opinion.
However, picking up a newer, bigger drive, and its tapes from ebay
will no doubt ease the road ahead. Tape changers are also nice,
but not a requirement. 120 meter DDS2 tapes are, when available,
very reasonable, I don't think I've ever paid over 4 USD per tape
when buying them in sealed tenpacks, brand new. I've NDI how that
translates to Norwegian money though, sorry.
Good luck!
--
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz 512M
99.19% setiathome rank, not too shabby for a WV hillbilly
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