whither /dev/CDisk?? [ WORMs vs. CD-ROMs ]

[Matt Taylor]

[ Sorry to cross post this, but I wanted to generate some thought on this
  subject. I've yet to hear some good discussion on where optical technology
  fits and where it doesn't. ]

In article <13212 at brl-adm.ARPA>, PAAAAAR%CALSTATE.BITNET at cunyvm.cuny.edu writes:
> The logical place for optical disk technology is to use
> it in place of Magnetic tapes
> (1) for distribution.
>   A CD-ROM is smaller, lighter, offline printable,
>   stores a vast amount of data,
>   and is very hard for the Postal Services to erase or damage.
> 
> (2)Write-Once-Read-Mostly Optical technology is an excelent replacement for
>   archival magnetic tape - about the speed I believe but better
>   volume and much harder to erase or accidently overwrite. I even think
>   that someone has a plug compatable Mag Tape replacement
> 
> Dick Botting (doc-dick)

Those are two very good, astute observations.  The standard misconceptions
are present however.  One of the more difficult things the general public
has yet to discern is the real, applicable difference between CD-ROM and
WORM (Write-Once-Read-Many. Yes, it used to be Read-Mostly but not any
more).

Barring the obvious technological differences, the CD-ROM has the
advantage of cheap, mass replication of data.  The WORM has the advantage
in flexibility and portability.  What??? portability you ask?  Yes.  True
portability implies the capability to exist and function through OS or
hardware changes.  "The data usefully outlives the machine that produced
it".  For example, that means taking your database originally created
under DOS (cringe), and "transparently" mounting it on something like a
Sun, Mac, VAX, etc.

Both types of media have a distinct and separate position in the market
place.  One needs to restrain from taking a new technology and forcing it
where it doesn't belong.  "Gee! Lets put our monthly financial records on
CD-ROM" or "Hey! Lets put our annual financial statement on a WORM and
make 10,000 copies for our shareholders".  Wrong.  It may seem obvious in
the extreme examples above, but it sometimes gets very confused by the
consumer and the manufacturer.  On the other hand, experimentation with
the technology in the market place is vital and needs to continue.

What does all of this have to do with the above quote?  (Finally!).  Well,
there seems to be some misconceptions between magnetic tape and WORM.  The
new 5 1/4" WORM products are extremely efficient and fast.  The typical
benchmarks show data reads being 92-97% of a 28ms hard disk.  Writes are
somewhat slower (the verify pass slows you down) and come in around
62-78%.  Combine that with the WORM's high density along with an
efficient, transparent OS interface and you have a really good, useful
product.  The key word here is useful.  If it's not useful, nobody (okay,
typically nobody) will use the damn thing. (Something to be aware of, disk
space efficiency is one of THE major components and usually the hidden
gotcha!).

Now we have a technology we can all use.  By looking at both WORM and
CD-ROM technologies and using them where they fit and avoiding using them
where they don't, you can achieve the maximum benefit of both.

Standard disclaimer:  I have nothing to do with WORMs except design and
write file systems for them and use them in my garden.

-- 
Matt Taylor @ Maximum Storage, Inc.    
Colorado Springs, CO.  303-531-6888   
{cbosgd,handel,hao,hplabs}!hp-lsd!frisbee!matt