From: dtb@adpgate.UUCP (Tom Beach)
Newsgroups: comp.periphs
Subject: Re: DAT vs QIC
Date: 11 Dec 92 17:45:48 GMT
Article-I.D.: treyvan.1796
Organization: ADP Dealer Services R&D, Portland, OR

: While researching tape backup options I came across an "editorial"
: by Richard Peters, Tandberg Data VP Marketing.  This short tome
: sings the praises of QIC technology and raises questions about the
: reliability of 4 mm and 8 mm helical scan technology for data backups.
: His arguments are (more or less):

Keeping in mind, of course, that Tandberg is a supplier of QIC drives
and therefore not exactly an impartial observer, 
of this whole picture, I tend to agree with him :-).

We use 8mm tape (Exabyte) on our products but the whole idea of running
backup media at the areal densities required by helical scan tape devices
leaves me in a cold sweat.

helical scan works just fine for video. Youd be hard pressed to notice a
lost bit in a video. A lost bit somewhere in a backup makes the rest of the
tape useless. If that doesn't scare you you've never had a hard disk fail


: 1.  DAT and 8mm tapes rust, QIC tapes don't (already an oxide)

Granted, metal partical tapes now have passivating coatings but his
fundamental point is well taken...
 
: 2.  QIC operates over a wider temperature & humidity range

True, but not that much really. The humidity is the big factor, and the
real point here is not so much wider range for recording environments
but that data retention over time should be far better with gamma
ferrous oxide tapes than with metal particle tapes. 

Would you like to be able to read your backup a year from now?

: 3.  QIC is more reliable - lower error rate, longer MTBF, etc.

I fear I have to quibble with him a bit on this one. As QIC drives it's
areal density up to put multiple GB on a single cartridge their error rates
are climbing also. I don't think this is a technological differentiation
but a recognition that QIC has been running at VERY conservative areal
densities.
 
: 4.  QIC can grow to 100 GB/tape, DAT is already near its limit,
: will require longer and thinner tapes.

In the battle over capacity, ultimately the media with the larger surface
will win. Granted, using helical scan gives 4mm/8mm a bit of an edge but
DAT is ~300' x 1/8", 8mm is ~350' x 1/4" (8mm will ALWAYS store more than
DAT: This is apples/apples). QIC is 1020' x 1/4"; that's nearly 3X 8mm
tape area and over 6X DAT tape area. DAT **CANNOT** and will not ever be
the long term capacity leader!!!!!!! 
 
: Does the DAT crowd have anything to say about this?

I'm interested in that myself....
 
: -- 
: Chuck Forsberg WA7KGX          ...!tektronix!reed!omen!caf 
: Author of YMODEM, ZMODEM, Professional-YAM, ZCOMM, and DSZ
:   Omen Technology Inc    "The High Reliability Software"
: 17505-V NW Sauvie IS RD   Portland OR 97231   503-621-3406

Tom B

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|  Tom Beach    :   Sr. Engineer   :     Mass Storage Technology          |
|  ADP Dealer Services                                                    |
|  2525 S.W. 1st Ave.                    phone : (503) 294-1541           |
|  Portland OR, 97201                    email : adpgate!dtb@apple.com    |
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Newsgroups: comp.periphs,comp.periphs.scsi