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From: simons@hpcpbla.HP.COM (Simon Southwell)
Newsgroups: comp.periphs
Subject: Re: Audio DAT recorders as computer backup devices
Message-ID: <1450009@hpcpbla.HP.COM>
Date: 15 Jun 90 13:04:47 GMT
References: <21987@megaron.cs.arizona.edu>
Organization: HP Computer Peripherals Bristol, UK
Lines: 72

> 
> In the last week or two it has come out that audio DAT recorders will
> be available here in the USA as early as September.  The prices will
> start out at $900 and on down, and will likely drop as more models
> and volume get on the market.
> 
> Could these guys be used for computer backup?  I guess that your are
> supposed to be able to make perfect copies of a CD.  This might imply
> that there is digital input/output in these beasts (or at least
> input - or else the CD player would turn the bits into analog, and
> then the DAT recorder back into digital.  Not a perfect copy in my
> book).

I know that the Sony DAT player (the DTC1000) has digital audio
input and output interfaces, based on the AES/EBU interface standard
(see "AES recommended practice for digital audio enginering --- serial
transmission format for linearly represented digital audio data. J.
Audio eng. Soc. 33, 975-984") much like that of the Digital OUT of a
CD. I also believe that digital copying of CDs cannot be made since
the DATs will won't recognise the 44.1KHz data (DATs nominaly work at
48KHz sampling). This is done only as a copy prevention measure,
rather than for any technical reason. Indeed, they now have a "copy
code" on pre-recorded material to prevent digital to digital copying
of DAT material. All this needed to be done before DATs were allowed
in the US.

Having said all this, in theory, the Digital interfaces could be
used to store and retrieve computer data. There are some drawbacks
however, such as 

  . Limited file searching facilities. The "Start" id's for tracks
    could be used, but you'd have to develop some equipment to decode
    all this properly.

  . Inferior error rate. The DAT has 2 levels of error correction,
    plus an interpolation circuit, for upto 8 uncorrected samples
    (never heard of interpolated data though :->). The Digital Data
    Storage drives can offer 3 levels of ECC, plus read-after-write
    data integrity checking, which in theory give an error rate of
    better then 1 bit in error every 10^15 bits.


> 
> If they could be used for this purpose, it seems that it could be
> cheaper than buying the DATs that are currently available for
> computer backup, just because of the large numbers involved.
> 

You are of course paying for all the extra electronics (ie.
controller, host interface etc.) on a Digital Data Storage drive, as
well as the better data integrity. But I believe that basic SCSI OEM
drives sell from around $1200, which isn't much more, and the price of
these drives is very much dependent on the audio market, since the
Head/mechanism technology is common to both DAT and DDS units.

So, I guess using a DAT as data storage is possible, but it may not be
worth it in the end. It all depends on the application I suppose.
I hope this is helpful.


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