seeking backup device advice

There are days when I wish tape drives weren't so sensitive to tiny bits
of lint. :-/ Obviously that's a forlorn wish, but it does make me wonder
if better ways to do backups exist these days. The quantity of data to be
backed up is small and would fit on a single DVD or a couple of CDs.

Are CDs or DVDs at least as reliable as tape for storing executable and
data files for 1 year? 10 years? [Assume the use of "archival quality"
CDs (or DVDs, if such exist).] Is there any error correction in the drives
themselves (my impression is "no"), or does driver or application software
have to do it?

I like the idea of a LAN-attached, instead of computer-attached, device.
Netgear (I think) has some kind of "200MB disk + backup" LAN server, but I
don't know much about it yet, and I don't need the 200MB disk.

I'm not inclined to use a backup-via-the-'Net service. I haven't ruled
it out, but I'd prefer keeping my data in my hands rather than trusing
encryption.

Suggestions? Recommendations? Things to avoid? Other options I should
consider?

Thanks very much in advance,
-WBE

wbe wrote:
> There are days when I wish tape drives weren't so sensitive to tiny bits
> of lint. :-/ Obviously that's a forlorn wish, but it does make me wonder
> if better ways to do backups exist these days. The quantity of data to be
> backed up is small and would fit on a single DVD or a couple of CDs.

> Are CDs or DVDs at least as reliable as tape for storing executable and
> data files for 1 year? 10 years? [Assume the use of "archival quality"
> CDs (or DVDs, if such exist).] Is there any error correction in the drives
> themselves (my impression is "no"), or does driver or application software
> have to do it?

The drives certainly have error correction. All CD/DVD data is written
redundantly. So you may have a buildup of problems over time that you
never notice until it finally is enough that the EC can't overcome it.

(I think the other question is how do you keep track of something to
make sure you can read the media in a long time.)

> I'm not inclined to use a backup-via-the-'Net service. I haven't ruled
> it out, but I'd prefer keeping my data in my hands rather than trusing
> encryption.

Besides "trusting encryption", you have to make sure you keep track of
the key. I consider the key management issues to be considerably larger
than the chance of someone stealing data by brute-forcing the encryption
directly.

> Suggestions? Recommendations? Things to avoid? Other options I should
> consider?

Your question made me search and come up with this document:
http://www.itl.nist.gov/div895/caref...dlingGuide.pdf

They suggest that long term storage of such media should be possible
under ideal conditions. Also, don't wait too long before using blank
media.

With tapes, the big worry is apparently that the substrate itself breaks
down or degrades somehow (I've heard tales of 8-track tapes that have
basically glued themselves together so that the tape couldn't be unwound
without damage). I've also been told that when a tape is archived for a
long time, the magnetic domains become more permanently magentized. So
there's less chance of the data disappearing because the magnetic data
changes, but you wouldn't want to use (or reuse) an older tape.

I also assume that being the niche market they are today, there are very
few 'cut-rate' data-grade tapes on the market (perhaps this is a
misconception on my part!). So you're almost always getting good media
(with the possibility of a bad batch always being present). With
CD/DVD, there's a *lot* of cheapo out there. You have to be more
diligent in selecting high quality.

Other links I found...:
http://www2.verbatim-europe.com/inde...d=1&cat_id=347

http://www.manifest-tech.com/media_d...patibility.htm

Details from German magazine test
http://cdrlabs.com/phpBB/viewtopic.php?p=142231#142231

--
Darren Dunham
Senior Technical Consultant TAOS http://www.taos.com/
Got some Dr Pepper? San Francisco, CA bay area
< This line left intentionally blank to confuse you. >

I asked:
>> Are CDs or DVDs at least as reliable as tape for storing executable and
>> data files for 1 year? 10 years? [...] Is there any error correction
>> in the drives themselves (my impression is "no"), or does driver or
>> application software have to do it?

Darren Dunham <> kindly replied:
> The drives certainly have error correction. All CD/DVD data is written
> redundantly.

That's good to know. Although I knew the data was written redundantly on
the media, I wasn't sure whether that was done by the drive itself or the
program writing the data.

>> Suggestions? Recommendations? Things to avoid? Other options I should
>> consider?

> Your question made me search and come up with this document:
> http://www.itl.nist.gov/div895/caref...dlingGuide.pdf

Thank you! I hadn't seen that before.

[Short summary of 50 page PDF file: optical storage *can* last longer than
tape under ideal conditions, but can also degrade quickly in the presence
of water / high humidity, or poor handling. In temperature-controlled
conditions of low 70s(F) and mid-to-low humidity with careful handling,
good original media, and no exposure to UV/sunlight, 5-10 years is entirely
possible. The bigger problem is technological obsolescence, so one should
plan to copy archival stuff to whatever the new, "current" digital media
format is every 5 years or so.]

> They suggest that long term storage of such media should be possible
> under ideal conditions. Also, don't wait too long before using blank
> media.

That, too.

> With tapes, the big worry is apparently that the substrate itself breaks
> down or degrades somehow (I've heard tales of 8-track tapes that have
> basically glued themselves together so that the tape couldn't be unwound
> without damage).

There's that, and, IIRC, there's also the opposite case of adhesive
failing.

> I've also been told that when a tape is archived for a long time, the
> magnetic domains become more permanently magentized.

Actually, I think the effect in question is magnetic "bleed through", where
the magnetization of rolled tape layer N modifies layers N+1 and N-1 and
vice versa. It's kind of like taking the original data and adding an
"echo" of what came K seconds ago and what will come K seconds from now
(where K is 1 rotation of the tape reel).

> Other links I found...:
> http://www2.verbatim-europe.com/inde...d=1&cat_id=347
>
> http://www.manifest-tech.com/media_d...patibility.htm
>
> Details from German magazine test
> http://cdrlabs.com/phpBB/viewtopic.php?p=142231#142231

Thanks!


On a separate, but related subject, Seagate just announced a new, record
recording density in the lab: ~250k tracks/inch with ~1.5M bits/inch per
track (IIRC). Seagate said when this technology reaches the market in
2009(?), 2.5 inch drives will hold 500GB, and 3.5 inch drives will hold
2.5TB. Assuming Blu-Ray disks hold 40GB, that's 63 Blu-Ray DVDs worth of
hard disk space!
-WBE