[Info-vax] TLZ7

[Richard B. Gilbert]

On 11/6/2010 5:38 AM, Kari Uusimäki wrote:
> 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.
>

I would lump the takeup leader with the rest of it.  My experience has 
been that DLT drives are high maintenance devices.  When they do succeed 
in making a backup, you can generally count on being able to restore it. 
  To be fair, tape drives in general tend to be high maintenance!