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

[urbancamo]

On Tuesday, 9 October 2012 15:03:06 UTC+1, Stephen Hoffman  wrote:
> 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

Just to add my 2 cents. Firstly, I don't disagree with anything said. I don't rely on DDS any more is healthy.

However, on a slightly different tack data longevity is perhaps less of an issue. I have read several DDS1/DDS2 tapes recently that were written in 1994 without any issues. 

My usage pattern for DDS is typically to only use an individual tape a few dozen times, so maybe that pattern has saved me from disaster.

Mark.