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Re: Backup

On 17/08/12 02:25 PM, Glenn English wrote:

On Aug 17, 2012, at 10:53 AM, Camaleón wrote:


On Fri, 17 Aug 2012 03:40:41 -0500, Emil Payne wrote:


I have a 1 TB external USB drive with 362 GB used. I'd like to do a full
backup to DVDs and then an incremental (or something) backup every month
or two, also to DVDs or CDs. I'd like the backups to be compressed in
order to save space (i.e. - the number of DVDs/CDs used).

Optical media storage is a PITA for big amounts of data (it's very slow
and hard to manage when you intend to do rewrite operations).

I really hate to be the old fogey here, but if you've got the $$, tape
sure does a good job. Use Amanda for both incrementals and fulls, and to
reduce PITA, get cron to run them overnight. Or over the weekend, if you
want to backup a lot of data, but infrequently.

Optical disks and hard disks don't last. I have audio tapes from the 1950s
that are still good. Tape has its disadvantages, but longevity isn't one
of them...

For backup, though, I'd suggest springing a little more media and telling
Amanda to write uncompressed tarballs -- for reliability and ease of recovery
from a major disaster. You can recover from an Amanda backup tape with nothing
more than plain old tar. A major PITA, but it's possible.
While tape has uses, it's not all that reliable. Tape is subject to chemical deterioration, magnetic drop-outs, stretching, and a host of other problems. You won't notice the problems so much on audio tape with a lot of tape surface to hold the music (1/2 inch open reel audio tapes from the 1950s are more reliable than cassettes from the 1970s). However, on data tapes, the problems start showing up fairly quickly.
It's main advantage over the years has been capacity. A automatic tape library can hold a lot of data over multiple tapes. However, tape changers are expensive, as are the media.
You're correct about not compressing the data. Uncompressed tars are less prone to catastrophic failure from data dropouts. However, this is less of an issue with optical media. Still, I always do a cmp after backing up to optical media just to ensure the data actually copied correctly. If it didn't, I rsync and cmp again.
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