DAT Tape drive reliability

[glenn at aoi.ultranet.com (Glenn Burkhardt)]

I have to admit that I was somewhat alarmed by reports of corrupted DAT tapes
in recent mail to the list.  It still seems to be an open issue to me, since
I personally haven't had any bad experience.

I've been spending a bit of time hunting on the web for evaluations of the 
different tape drive types available, but haven't found much.

The DLT drives are said to be by far better, but the price of the HP 40gb drive
at Insight is $2800, as compared to the HP DAT24 (12gb raw) at $785.
MTBF for the DLT drives is 200,000 hours at 100% duty cycle, and 200,000 hours
for DAT drives, but at 12% duty cycle.  One report mentioned 2000 hours for the
head life on DAT drives.

The Sun Manager's mail archive is full of notes about the importance of keeping
the heads clean on the helical scan DAT drives.  They also seem to think that 
there are differences in cleaning cartridges.  The cleaning cartridge I have
recommends cleaning once a week if one tape per day is used (I haven't been so
diligent!).  

One survey from the mailing list archive had this summary on different models:

Drive                   Report

Archive Python          problematic
Sony SDT-7000           Problematic
HP C1533A               Great drive
HP 35480                Problematic

but it was dated 1996, so the information isn't current.

Another page had this advice:

"The DAT media tapes are also not as resilient as DLT tapes, and keeping the
heads clean in a DAT drive is imperative to maintain error-free backups. So if
you are running continuous 18-hour system backups, give strong consideration to
a DLT drive."




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