On 2007-02-28 21:09, Alastair Neil wrote:
> I have a question regarding how best to manage backups to vtapes and
> archival onto tape media.
>
> First a little history, I used to have a DLT4 9 tape changer and have
> been running my backups through this for about 3 years now. This
> changer failed and for a number of reasons was not under support.
> Fortunately I had a scalar 24 LTO2 changer I can use. However our
> nightly backups were running around 40-60 Gbytes so unless I could
> append to tapes this would waste a lot of media.
>
> The solution I would like to implement is a series of vtapes each about
> 30Gbytes and a script to check how much had been used and initiate an
> archival dump to the LTO2 media if it is in the vicinity of 200Gbytes.
>
> So this brings me to my few questions
>
> In order to prevent older tapes being overwritten before being stored to
> tape is it best to basically never reuse a tape and have the script
> erase and relabel the slots after the archival dump is made?
>
> I would need two amanda configurations to manage this kind of
> configuration. This lead me to worry about recovery - how do I locate
> the correct archival tape to find the correct tapes for the daily dumps?
>
> I have read through the File driver page on the wiki.zamanda.org
> <http://wiki.zamanda.org>, but I did not see any specific information
> about these questions. Am I being dense?
My main requirement for a backup system is that the restore procedure
should not be too dificult. Ever had a system crash, and working
hard to restore stuff, while the phone rings with angry users?
Anything making it more complicated than necessary is to be avoided!
My first impression for such a setup is that you're making the
restore much more difficult. What you have on tape is a series
of amanda-vtapes. Restoring then consists of first locating
the physical tapes, which contain the correct vtapes, restoring
those to some temporary location, and then extracting the files
themselves from those vtapes. The "restoring to a temporary location"
also makes it impossible to use the normal amanda tools on these
restored vtapes.
Note that the indexes amanda generates for the physical tape, consist
only of the filenames of the vtape-implementation. By erasing and
relabeling the vtape slots, you also erased those indexes. Getting
a consistent set of vtape-indexes + vtape-contents stored, plus making
those usuable for a normal restore with amrecover is not trivial.
If you believe your disk is reliable enough to hold many days of
backup data, why don't you just declare it as a large holdingdisk.
Just run Amanda daily, and let the backup images collect on the
holdingdisk. When enough backups have been collected, insert
a tape and run amflush, or just let it flush to tape during the
nightly amdump run (with "autoflush true" in the amanda.conf file).
This procedure lets you use the full possibilities from amanda,
including restore with indexes from holdingdisk or tape, and
let amanda worry which tape or holdingdisk image contains which
files.
One more contemplation: is your backup data really that worthless
that you cannot afford 5 LTO-tapes extra, so that you can
still backup daily to tape? Just calculate the cost when you
do loose the backups of the last 3 days, because you tried to
economize in the wrong place. Don't try to economize in the
wrong place. Look at it this way: because you don't have to
spend a fortune on a commercial backup solution plus some
small fortune on yearly support and upgrade, you can now invest
some more money in physical tapes, and still do it cheaper and better.
--
Paul Bijnens, xplanation Technology Services 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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