Re: Does amanda only backup changes to files?

Dean Pullen wrote:

If amanda makes this incremental backups of changes, is it then possible to
retrieve multiple past different backups from one tape?


Not from one tape.
The second run overwrites the dumps from the previous run.
Amanda currently insists on one tape for each run. Workarounds
exist by dumping to a large holdingdisk (without tape in the drive),
and flushing collected backup images to tape.

If so, how?

-----Original Message-----
From: owner-amanda-users AT amanda DOT org [mailto:owner-amanda-users AT amanda 
DOT org]
On Behalf Of Dean Pullen
Sent: 07 January 2004 13:08
To: amanda-users AT amanda DOT org
Subject: RE: Does amanda only backup changes to files?

Yes I simply overwrote the tapelist so that I could perform a secondary
backup for testing purposes only.

I thought I had a problem with amanda, so thanks for the information.

-----Original Message-----

From: Paul Bijnens [mailto:paul.bijnens AT xplanation DOT com]Sent: 07 January 2004 13:09

To: Dean Pullen
Cc: amanda-users AT amanda DOT org
Subject: Re: Does amanda only backup changes to files?

Dean Pullen wrote:

I've been using amdump manually to test Amanda, and am backing up a full
disk's file system (/dev/sda). The first time its run it produces a report
with several gigabytes worth of backup:

USAGE BY TAPE:
 Label              Time      Size      %    Nb
 VFDailySet01       0:08    3393.4    4.1     1

Repeating runs on the same tape after this backup, seems to produce very
tiny backups:



On the same tape???   How did you force amanda to do that?
I hope you realize that the second amdump run overwrites the tape.
Ok.  It's just for testing, but you can test a restore with this
test...

USAGE BY TAPE:
 Label              Time      Size      %    Nb
 VFDailySet01       0:00       0.2    0.0     1

Does amanda only save 'changes' to files, or is something incorrect
happening here?



Amanda does not do the backup.  Amanda is the scheduler of backups,
and runs the OS dump program or gnutar.  And both these programs have a
notion of "incremental":  everything changed since last run.  They both
do this on whole files, not parts of files.
Incrementals can be done in levels.  Level 0 is the initial full dump.
A level 1 is all files changed since the last level 0.  A level 2 is
all files changed since last level 1 etc.

One of the most important parameters to amanda is how often you want
to schedule a level 0 (full) dump.  See "dumpcycle".
If you executed the two amdump runs one after another, then, yes,

the second run has much less to dump than the next, assuming yourdumpcycle is greater than 0. If you specify "dumpcycle 0" than this

indicates to amanda to schedule a full dump allways.



--
Paul Bijnens, Xplanation                            Tel  +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM    Fax  +32 16 397.512
http://www.xplanation.com/          email:  Paul.Bijnens AT xplanation DOT com
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