[H-GEN] Linux Backup

[Robert Brockway]

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On Fri, 9 May 2003, Jason Parker-Burlingham wrote:

> * Some people don't like to use even software compression because they
>   worry that an error on the tape will invalidate all the data in

Yes, this is the reason I don't like using it when backing up to tape.

>   later blocks.  In my experience software compression allowed me to
>   back up much more data than otherwise and never gave me a moment's
>   trouble; surely if something is wrong with the media or the drive,
>   then you're up the creek anyway?

With an uncompressed backup you risk losing one file.  With a compressed
backup you can lose considerably more than that.  In the end it is risk
assessment but I've seen far too many tapes (and drives) return errors to
feel comfortable software compressing to tape.  On the whole I've gone off
tapes as a backup solution anyway.  Too many problems overall.

Getting back to compression, there is a middle path here - the zip utility
compresses each file individually before archiving.  This is the reverse
to tar.gz of course. If you zip each file before writing it to tape you
will get some compression and still have the safety of individually saved
files. In general zip does not compress as well as gzip or bzip2 of
course.

Interfacing zip with dump or tar to get the desired result is left as an
exercise for the reader.

> * Whatever you do, *never* turn on hardware and software compression
>   at the same time:  instead of compressing the data even more, the
>   hardware compression will only make the data slightly LARGER than
>   before.

Agreed - they often get in the way of each other.

Cheers,
	Rob

-- 
Robert Brockway B.Sc. email: robert at timetraveller.org  ICQ: 104781119
Linux counter project ID #16440 (http://counter.li.org)
"The earth is but one country and mankind its citizens" -Baha'u'llah

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