On Saturday 01 May 2004 23:51, Justin Gombos wrote:
>I was looking forward to using Amanda to backup 4-5 machines on my
> LAN and one over the Internet, but something seems incredibly
> stupid about the way Amanda forces the user to operate.  Please
> tell me I'm wrong; maybe I'm misunderstanding the documentation. 
> If I want to perform daily backups to CDRs, and I expect to have
> around 10 megs of data change per day, do I really have to waste an
> entire CDR every day?

In order to do an incremental, there must be a full level 0 of that 
same disklist entry to be used to determine whats been changed and 
needs the incremental to be recorded.  That means that your 
relatively small 700Mb cd-r is probably going to be too small to be 
really usefull.

There are both dependability and security reasons why amanda must use 
a different media each day, and they are not what one could call 
"open for discussion".  Much of this came about because of the lack 
of random access to a tapes contents, and because the tape itself may 
be ejected (which will rewind it) in between sessions by someone 
unknown to the operator or to the crontab entry that runs amanda.

These individual media may be re-used according to the tapecycle 
setting in the file amanda.conf when their "time on the shelf" has 
expired by having used up all other "tapes" in the tapelist, at which 
point the oldest one becomes todays media.  There is another name in 
this amanda.conf, "dumpcycle", which tells amanda how many days she 
has to do a full backup of every entry in the disklist, typically set 
for 7 days.  And yet another, "runspercycle" which you would set to 5 
if no backups are done over the weekends, and amanda uses this to 
tell her that even though 7 days is the time limit, she only has 5 
actual runs in those 7 days to get it all done in.

Amanda will, given enough time, work out her own schedule that will 
achieve this AND attempt to balance the amount of media used so about 
the same amount is used on each run.  Breaking the disklist up into 
many smaller subdir entrys and using tar, not dump, allows amanda to 
do a much better job of balanceing the media usage.

To demo how well that can work, I have about 65Gb of data on 2 
machines here, and I'm using a 4Gb (DDS2) tape in a 4 tape changer, 
one tape a nightly run.  dumpcycle is 7, runspercycle is 7, and 
tapecycle is 28.  Typically amanda will do about 3.6 gigs of mixed 
fulls and incrementals per nightly run, so it all fits on the one 
tape I allow her to use.  Having a changer, I could let amand use 2 
or even 4 tapes a night, but the write time for 4 tapes would be well 
into the next day with these slow tapes.  Also be reminded that 
amanda cannot span a single disklist entry across 2 tapes, but will 
restart the failed entry on a fresh tape if allowed to use the 
changer, another argument in favor of smaller disklist entrys.
I use compression only on those disklist entries that will compress, 
no use wasting cpu time to do the compression on a directory full of 
tar.gz stuffs.

Amanda is now learning how to use media other than tape, read the docs 
for details on that.

Amanda can do one heck of a job safeguarding your data, but amanda 
doesn't always take well to being bossed around.  Most of us don't 
try once we understand how amanda works.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
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by Gene Heskett are:
Copyright 2004 by Maurice Eugene Heskett, all rights reserved.