[Info-vax] TK50 - this is annoying...

[Stephen Hoffman]

On 2012-10-09 10:08:09 +0000, Johnny Billquist said:

> On 2012-10-09 03:59, Paul Sture wrote:
>> 
>> Shudders at the thought of relying on DDS-3 for all backups.
>> 
>> BTDT. Got bitten. :-(
> 
> :-)

Yeah.  Bad Idea.

> I regularly verify them, and so far no problems. But I have seen a 
> large number of failed drives at places...

The head-pass count rating on the DDS media makes it nearly write-once 
read-maybe media, particularly around the tape headers.  (IIRC, 2000 
passes.)

There's a reason that DDS media and DDS gear is cheap, after all.

That head-pass rating wasn't far off of empirical, either.  I got maybe 
a week's worth of use out of each cartridge.

That was using the cleaning cartridge at the recommended intervals.

Verifying?  That's just scraping off a little more of that precious oxide.

Count up a tape mount and multiple BACKUP and MOUNT-DISMOUNT sequence 
sometime.  Add in verifying, if you're inclined.  You can visit the 
tape heads a number of times with a multi-disk backup to a single DDS, 
if you're not really careful about how you handing the mounting and 
dismounting and BACKUP commands in your DCL.  Pretty soon, you're close 
to the head-pass rating (assuming that rating even matches la realidad) 
and off slides your data.

I scrounged and switched to DLT an aeon ago, and never looked back.  
DLT, SDLT and LTO are vastly more reliable, barring your having 
acquired an average box of crap-grade recording media.  (There's a fair 
amount of that around, too; counterfeit or just generic-brand dreck.)  
Even the fossil-grade TK50, if you have "current" firmware and one of 
the second-generation hammerheads, was more reliable than DDS.  
Nowadays, scrounging a decently-less-than-ancient SDLT or LTO is 
trivial.

Cue my usual "upgrade" discussion.

-- 
Pure Personal Opinion | HoffmanLabs LLC