[Info-vax] TLZ7

[Kari Uusimäki]

On 5.11.2010 2:06, Alan Frisbie wrote:
> On 11/4/2010 3:40 PM, Kari Uusimäki wrote:
>
>> DLT, SDLT or LTO tape drives are very reliable and have much better
>> performance and therefore they are mostly used in production
>> environments.
>
> In general I would agree with you, but I have experienced a
> tape failure rate (with new tapes) between ten and twenty percent.
>
> Once they have been successfully used, they seem to stay good for
> many more uses, but I never trust new tapes. This applies to
> both SDLT-1 160/320GB and SDLT-2 300/600GB tapes. Just last
> month I bought ten of each, and two in each batch were bad
> (parity / CRC errors).
>
> With DAT tapes, they generally failed with crinkled tape
> hanging out of the cartridge, but I didn't have much of a
> problem with parity errors as long as I regularly used the
> cleaning tape.
>
> Alan "The other AEF" Frisbie

I do agree about the bad tape quality. I've also seen tape failure with 
the newest tape types (SDLT and LTO). I haven't investigated the reason 
to the failures, but because most tapes stay good for years of 
continuous use I suspect the quality is varying. Especially because the 
failure rate of new tapes is high.
Of course the new tape types with extremely high density and 
microscopous particles are more sensitive to dust and other contaminats 
than older tape types.

The complex mechanical design of the DAT (and the AIT) tape drive causes 
the tape to wear more than with the more straightforward designs (DLT, 
SDLT, LTO). The amount of moving parts in the DAT mechanism also causes 
failures.

Btw I haven't seen a single mechanical failure (breakdown) of a DLT 
drive (or the predecessors; TK50 and TK70) during the 20 years I've been 
in this business. The parts wearing out are the take-up leader and the 
read-write head, but the construction is otherwise so sturdy that it 
surely is capable of running hundreds of thousands hours.



Kari