[Info-vax] TLZ7

[John Wallace]

On Nov 6, 9:38 am, Kari Uusimäki
<uusim... at exdecWITHOUTTHISfinland.org> wrote:
> On 5.11.2010 2:06, Alan Frisbie wrote:
>
>
>
> > On 11/4/2010 3:40 PM, Kari Uusim ki 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

In my experience quite a few TK50s and TK70s failed due to less than
ideal user interface design (specifically for tape unload), but once
the users were educated not to attempt to raise the handle till the
drive was in the right state, DLT drives were far more reliable than
DAT.