Re: DVD RAM?

Previously J. Clarke <jclarke.usenet@xxxxxxxxxxxxxxxx> wrote:
Arno Wagner wrote:

Previously J. Clarke <jclarke.usenet@xxxxxxxxxxxxxxxx> wrote:
Pete wrote:

Hi

I have read that DVD RAM is a much more reliable media for important
backups. However I cant seem to see any drives that take the media in
their cartridge, only DVD re-writers like the GSA 4167b that mention
DVD RAM but pressumably use the type 4 cartridge with the disk removed.

Can anyone recommend makes/models that use the disks in their caddies?

You're looking for older SCSI drives. Ebay is your best bet, brands
would be Pioneer or Plasmon (not sure if Plasmon made drives or just
relabelled Pioneer).

The chemistry of DVD-RAM is the same as for DVD-RW, all that is different
is
the formatting. There's no real reason to believe that DVD-RAM will be
any more durable than DVD-RW, its main advantage is convenience--DVD-RAM
is designed for data storage and can be treated like just another disk
without kluges such as packet-writing.

Actually there is a serious advantage: RVD-RAM uses verify on write
and does defect management.

Verify on write doesn't mean that the data is going to be there a year down
the road when you need it. The big problem with DVD as an archival storage
medium is the stability of the chemistry, not the integrity of the writing
process.

Actually verify on write deos help massively, as it identifies whether
a write was good or not. Doing it in software is not the same. If
the drive does it, it can use higher standards for successful verifies
than for standard reads. You are correct that it is not the only thing
that guarantees long-term readability. But chemical stability, once
assured, is not the main reliability problem of optical media. Dust,
areas gone bad, vibration, etc. is. For example I had one MOD that
had > 900 reallocated secotrs, because dust got into the cartridge.
Write only these would all have been potentially unreadable sectors,
possibly after some time (since the initial write could have been
borderline, but a slight degradation could have made them unreadable).
But the drive identified them on write and made sure that all data
was written well. And at the end that I was informed that tha last
write was not successful. I happen to know that this was dust, since
after cleaning and reformatting the same MOD has worked well and
reliably without significant additional defect sectors for several
yeras now. True, MOD is not quite the same chemistry as DVD-RAM,
but long-term stability is not really an issue with the chemical
structure if the disk was manufactured according to standard (a
real issue with El Cheapo DVD-RWs!).

There is A;sp a second thing: MOD/DVD-RAM are factory certified and
have an initial defect list, were the manufacturer found weak
spots with _very_ sensitive equipment. No such certification is
done for DVD-RW.

There is also a second serious advantage:
The cartridge.

Which protects against scratches but does absolutely nothing to make the
chemistry more stable.

As I said the chemistry is not the issue with DVD-RAM.

Scratches are relatively easy to fix--there's a lot of Lexan there
to work with.

That may be a bit naive. Who has the time to polish their disks?
And what about dust, fingerprints, accidentd (drops, not correctly
aclingned in closing drive, ...)?

The main real-world benefit of the cartridge IMO is
that it gives you a way to put an easily readable label on a
double-sided DVD-RAM. By the way, the cartridge does little to
protect against spills--first time I saw an optical disk
demonstrated the salesman to his dismay couldn't get the drive to
read it. While he was off in search of techs I idly examined the
cartridge, opened the slider, and found that it was full of several
day old coffee.

Not an issue. Jous clean it off with soap and water. The data is still
there.

Further, the cartridge is not required for something to be a DVD-RAM.

Yes, and the stated reliability drops dramatically for the formats
without cartridge, or once a disk has been removed from cartridge.

If you want durable random-access media in that capacity range you would
do better to go with magneto-optical.

Agreed. DVD-RAM was intended to be the MOD succesor, but it is not
up to it. I have all my important stuff on 3.5" MODs. Usually two
copies. So far I have not los a single bit in 7 years using
this technology.

Would you have lost any of it without that technology?

1.) Yes.
2.) Backups and archiveing would have been far more work and worry

Floppies: About half of my older 3.5" floppies were unreadable
when I backed them up 2-3 years after they were last used.
CD-R: First loss after 2 week on a disk that verified fine.
Numerous other losses or parial readabilities. And
a bitch to use.
CD-RW: Disk that verified fine in the writing drive, but was
unreadable in others. Also see CD-R.
HDDs: Two deathstars and two fried Fujitsus (the second my
mistake). The deathstars with warning signs to late to
get all data off.
Cheap tape (Quic-80): A nightmare. Compares that did not compare.
Tapes that were unreadable after a few weeks.

I have no experience with professional storage tape, but I
expect it comes on par with MOD for reliability, has not as
long data lifetime (say >10 years) and is far cheaper per byte
and far more expensive per installation.

Yes, I would have definitely lost data. Unless I had installed a
rigorous "3-copies and check each every year" regiment for my
backups. In contrast MOD is a "write and forget" technology, that
does not require any drivers or special softwware and will reliably
keep your data/family photos/stuff you care about safe for decades.
(Most vendors say > 50 years, a Phillips engineer told me probably
80 years, but there the acceleraded ageing models were getting
shaky...).

Interesting side note: In Japan MOD is all the rage. Seems people
there have more of a long-term outlook on storing data.

Second side note: In medical imagery, the law here requires the
images to be kept available for 20 years. It seems all the
scanners use MODs for this.

Arno
.

Relevant Pages

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  • Re: DVD RAM?
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