From: Dan Dugan <>
> So far as I can tell, what you call "real optical" is MO;
> magneto-optical. We've been through this before. Because of the
> educational function of this list, I implore you to use accurate
> technology.
I guess I'll have to start running everything by the experts before
posting. I did not realize there would be a test. Or that I was
publishing in a scientific journal. And as for the educational value of
this list, I have some serious doubts. Enough of that though.
Note that although the 3.5" disks that I use are MO, not all that I
consider real optical is MO. In the larger disk sizes there are several
methods used. So using MO to designate what I'm talking about would not
be correct terminology.
I say "real optical" to distinguish from Apple's new terminology, in
which CD-R is "optical". And before you get upset, yes I know that CD-R
is a form of optical disk. A simplified system, and the simplification
made the risks of failure greater it appears. The opticals I'm talking
about were designed with the primary purpose being archives. That, more
than anything else is what distinguishes them.
>>>I do maintain a copy of my stuff on audio CD as well. Seven years and
>>>counting, and none of those have failed. Audio CD is not a computer tied
>>>format, so has a greater chance of surviving longer as a format. I am
>>>very careful how I burn them.
>
>
> My CDRs in audio and CD-ROM formats are the same age and still good.
> I second the motion about being careful; the big problem now is
> finding stock optimized for robust quality rather than speed. I just
> found 200 older CDRs in Canada, from a dealer who sold them off cheap
> because they were old! That'll cover my mastering for a couple of
> years.
I recently bought some CDR blanks off a pallet load of them that a local
supplier has. Same as the good, slow writing HHb blanks. I've not had
time to test them much yet. These are also not current blanks.
Funny thing, I had a few unused blanks from seven years back that I
recently discovered. The coating on all of them (sony & fujitsu) has
gone bad. The same blanks that were recorded are just fine with no sign
of the same problem.
>>>And, of course since I record on MD, which is about as good as real
>>>opticals, I file away the originals of those too.
>
>
> MD is also a magneto-optical disc. I think one long-term stability
> factor might be how small the recorded track is. I note that data MD
> discs hold 140MB. I assume audio MDs use the same track pitch. Given
> 5X audio data compression, that would give the equivalent audio time
> of 700MB, which is CD-size. An MD is about a 2.5" MO disc.
The MD uses a formed track on the disk. It's MO, but a different coating
than the 3.5" MO's. And a thinner base stock. I believe it uses a
different reading method too. It was that I had lots of experience with
the 3.5" MO that attracted me to the MD in the first place. Like the
3.5" MO, I have not had a MD disk fail.
> I note in dealer listings that 3.5" MOs can be bought with capacities
> from 128MB up to 1G. What capacity do you use? Do you think the
> smaller capacities have wider (more reliable) tracks? Are the drives
> made in different capacities, or is it just the disc?
Max capacity is up to 2.3Gig.
http://www.fcpa.com/products/mo-drives/
The drives are designed for a certain level, but are always backwards
compatible. A 2.3 Gig drive will handle any of the disks back to the
128MB. However, a 640meg drive won't handle the 1.3 or or 2.3 Gig disks,
for instance. I still use my original 128's in my current drives. Only
thing you have to watch for is that the older disk formats can sometimes
give modern OS's trouble. Any of my disks that have not been used in a
while I'll usually copy everything off them onto my HD and reformat them
to keep them current in that. I should note that no mac format I've used
has become unreadable for this reason, usually it's just slower to read
or write.
Disks sizes: 128meg, 230meg, 540meg, 640meg, 1.3gig, 2.3gig All look
just the same, kind of like a floppy in appearance, but twice as thick a
shell. And of course the disk inside is quite different.
I have drives all the way back to 128's, they simply never go bad. Mine
are all Fujitsu drives, though some were originally repackaged by some
company or another. My highest capacity drive is a 1.3gig, which I have
a SCSI one internal in my Son's G4, and a Firewire "floater". But, what
I use currently is mostly 640 meg opticals, as they can be had off ebay
cheaply from time to time. I have a 640meg drive internally in the zip
drive bay of my G4, and a second one externally, both SCSI drives. The
larger sizes of disks have to be bought at full retail, making using
them more expensive. I recently won a ebay auction for a bunch of used
disks, turned out to be the entire archive of a dead graphics company.
Was listed on ebay as 50 disks plus, but ended up being more than 500
disks ranging from 128's to 640's with over half being 640's. Nearly all
sony or Fujitsu disks. So I'm set for some time. As a bonus I can amuse
myself looking through all the ad graphics before reformatting them. I
already had a couple hundred blanks here accumulated off ebay. So I'm
set for a fair while.
It's kind of hard to evaluate which is more reliable when every size of
both disks and drives has been 100% reliable. What do I say, one is more
perfect than the other? I've had zero disk or drive failures. I've not
read anything to indicate a difference. That's a exercise for the
technical hobbiest. I just use them, I don't dissect them.
Note you can corrupt what's written on them, just like you can on any
disk (they are rewriteable). So, once a archive disk is filled I set the
lock tab. That makes it a read only with very little chance of failure.
>>>...The future will remember this time period as a blank. Little will
>>>survive out of it in the way of graphics, sound, text etc. Because so
>>>little thought is given to preserving it for the future. We have the
>>>actual photographic negatives and prints from the civil war. How much of
>>>the computer/digital camera photographs will survive that long?
>
>
> A word to the wise...
But heard by few, and taken to heart by even less...
Walt
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