[Coco] Possible CoCo Bulletin Board forum
gene.heskett at verizon.net
Thu Dec 25 11:28:29 EST 2008
On Thursday 25 December 2008, Steven Hirsch wrote:
>On Wed, 24 Dec 2008, Gene Heskett wrote:
>> This is pretty much it for mailing lists for the coco. And its one list I
>> don't expire regularly. So my corpus of email from this list goes back to
>> Dec 2001, when I had to reinstall after a drive failure and wasn't able to
>> recover from the crappy tape system I was using for backups then. Now I
>> use virtual tapes on a big hard drive, and that appears to be at least
>> 100x more dependable than DDS2 tapes ever were.
>Sorry you found out the hard way about rotary-head digital tape drives.
>My experience with both 4mm and 8mm DAT suggests you can achieve similar
>results by simply making a "backup" and throwing the tape away :-(.
Mine wasn't that bad, I still have tapes I made on the amiga that were
readable under linux the last time I had a working drive. IMO the problem is
the inherent short life of the head drums, rarely over 1000 running hours.
In other words, no better than a typical vhs head. I tried to obtain
replacement heads from seagate, but they refused to sell me a head, or any of
the calibration tools. I felt that was nearly the ultimate insult because at
the time I was replacing a dvc-pro head at least weekly in one of the many
machines we had at the tv station. IIRC 22 of them at the time. And if
you've never seen a dvc-pro head, the DDS heads are truely monsters in
comparison, spinning at 1/8th the rpms IIRC. The dvc-pro head is almost the
size of a quarter and costs nearly 3 grand now-a-days, the toolkit is about 7
grand plus the tapes, 3 of them at $500 a copy.
The format was and is a good one, heads typically lasted 4-7k hours, which was
3.5-6.5k hours longer than the thousands of teeny little electrolytics that
were surface nounted in those machines. The largest was pencil eraser sized.
I started tossing them in a 3 pound coffee can, and by the time I retired,
was on the 3rd can. I miss that part of the job with the same enthusiasm as
I'd have for a broken ankle.
Now we have a couple of them still running for archival retrieval, but even
the news cameras record to hard drives treated as cassettes to get it to the
editors and ready for air. Many times more dependable.
>If you are ever interested in a reliable tape system, pickup a DLT IV
>drive and media from eBay (dirt-cheap, generally). These are
>stationary-head systems with very sophisticated tape handling (e.g. no
>pinch roller, no pressure rollers nor rubber of ANY kind involved).
>It's seriously difficult to kill data on a DLT cartridge. I've personally
>seen cases where tapes run over a bulk eraser were still readable! The
>drives use read-after-write to ensure integrity and will redo any blocks
>that fail CRC (up to a limit). The lack of read-back is a serious issue
>for the rotary-head transports which are mechanically incapable of it (at
Bulk erasers don't have the cajones to erase a data or vieo tape unless it
says Garner on it.
Anyway, the virtual tapes, on a 500GB hard drive, are many times more
dependable, I've not lost a byte since. And I don't worry about backups, I
have a user named amanda who runs herself evey morning at a little after 1
and does all that without any interference from me.
The drives I was using, the Seagate 4 tape changer, did I believe have
readback. There are 6 heads on the drum in two groups of 3, opposite sides.
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
The early bird gets the coffee left over from the night before.
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