Linux and Tape Backups

[Jerry Feldman]

On 08/26/2010 09:07 AM, Chris O'Connell wrote:
> Hi Everyone,
>
> I have recently found a box of tapes in our server room.  I would like =
to
> utilize these tapes to backup a server that I have running Snort and Na=
gios.
>  The server is presently backed up to a simple flash/thumb drive.
>
> I've erased the tapes using the *mt* command.  I then rewound the tapes=
=2E  I
> have a variety of questions:
> 1.  Does the mt -f /dev/st0 -erase check the tape for bad sectors/spots=
?
> 2.  Is there a way to list the contents of the ENTIRE tape?
> 3.  What is the best way to backup the entire disk (including SQL
> databases)?
>
>
>  =20
(1) WRT mt(1). AFAIK, the mt command does not scan the entire tape. Tape
formatting is much different than disk formatting. Essentially, you can
have multiple blocks on a single tape with eof marks at the end of the
current data block. So, you can perform a backup, leave the tape
positioned for another backup, etc.

My personal experiences with tapes has been very negative. While working
at a bank I found that not all the backup tapes were usable even though
they were kept in an environmentally controlled tape library. I had one
case where the tape drive (commercial reel-to-reel burned a hole in the
tape. My home backup tapes when I used them also were problematical.
When I had to restore some data, I found the tape was bad, fortunately,
I also had a Jaz drive and was able to recover. Commercial tape drives
are much better than the home junk.

(2) Yes. Normally when a tape is written it contains a label. How this
is set up depends on the software you use to write the tape. You can use
the mt command to forward space through the tape to look at labels.

The advantage of a tape (assuming it is a commercial grade) is that it
can store large amounts of data in a relatively small space that you can
store in a drawer, and is less sensitive to things like power surges and
lightning that can destroy disks. The disadvantage is that it is serial
media. Some backup software systems maintain (or used to) an index block.=


Thumb drives, IMHO, are not good backup tools as they can very easily be
destroyed or lose data over time. I would recommend a USB disk drive.
2TB USB drives are relatively cheap and highly reliable. The big
advantage of using a disk drive as a backup media is that data is much
easier to recover than from tape. Good NAS systems can be obtained for
under $2000 depending on the brand and amount of storage. At work we use
a cheap WD Mybook II with 2-2TB drives in a RAID I configuration. I use
rsnapshot to back up our systems, all under Linux. Overland's SnapServer
is one of the better ones as is Netgear's ReadyNAS. The advantage of a
NAS as a backup device is that you can easily monitor the health of the
drives and the backup data is always online.

--=20
Jerry Feldman <gaf-mNDKBlG2WHs at public.gmane.org>
Boston Linux and Unix
PGP key id: 537C5846
PGP Key fingerprint: 3D1B 8377 A3C0 A5F2 ECBB  CA3B 4607 4319 537C 5846