Re: Camera in rain and is hosed - what do I do?

On Mon, 17 Sep 2007 14:46:36 GMT, King Sardon <ksardon@xxxxxxxx> wrote:

On Mon, 17 Sep 2007 03:59:15 -0400, ASAAR <caught@xxxxxx> wrote:

On Mon, 17 Sep 2007 04:10:54 GMT, King Sardon cursed:

On Sun, 16 Sep 2007 11:30:18 -0500, Allen <allen@xxxxxxxxxxx> wrote:


Thank the Lord for CDs.
Allen

I curse CDs. Some develop errors in less than a year, and a small but
significant fraction are completely unreadable in 2 years. Anything of
mine that is important gets archived on an external HD. I know others
do that too.

Backing up to an external HD can be worthwhile and I do that too.
But I think that you're overly critical of CDs. Last week I checked
a batch of CDs burned over 3 years ago. They contained about 1,000
files amounting to close to 10GB of data. At the time I was
foolishly relying on the backup software's after-burn verification,
which I eventually discovered was hopelessly flawed, reporting no
errors even when several files weren't backed up at all. (I later
started doing a post backup CRC compare of each file.) Out of those
1,000 files, all but one were successfully copied back from the CDs,
which were a mix of ordinary Fuji and HP CDs bought in Staples, and
kept in sleeves within inexpensive zipper binders. For all I know,
that one bad file might have been bad from the start.

That a "small but significant fraction" became unreadable so soon
is unacceptable so I can understand why you don't trust CDs. But do
you know what caused the bad copies, and were the disks thoroughly
tested after they were burned? Sometimes insufficient hardware can
cause problems with CD reliability, and I was fortunate in using a
CD burner that had a SCSI interface, but only an old Win95 computer
(180 or 200mhz Pentium Pro CPU) was used, which probably didn't
compare favorably with whatever computer you and most other people
were using just a couple of years ago.

As far as hard drives are concerned, I wouldn't consider using
only one for backup purposes, as the odds that they'll eventually
fail is insufficiently close to zero. Several backup drives are
good enough for me, but even several hard drives are insufficient
for critical, irreplaceable business data, which really need *many*
backup tapes, to allow recovery of data that might become corrupt,
propagating to all of the backup hard drives before any of the data
corruption is noticed.

Just last week I needed to access some files on a CD that was burned
late November 2006. One file out of 17 was unreadable. That's
unacceptable, if you ask me--after only 10 months (and some people
still think CDs are for archiving). This was a business CD given to me
by a business associate, so don't talk to me about read-testing right
after burning.

Previous experience shows that sometimes 10 CDs will all read okay,
but other times there will be one or two bad disks in such a batch.
DVDs seem to be a bit better, but I don't have statistics.

Because of these bad experiences with CDs, I now archive almost
entirely on hard drives. The chances that a HD will crash in a given
year is very small. The chances of two going bad at the same time is
vanishingly small. If your data is on 2 HDs, it is safe from read
errors, even if not necessarily from fire/flood/theft.

KS

It's not a problem with bad CDs generally, it's a problem with operator error
and not knowing how the recording process works. CD/DVD burners have a
life-expectancy due to the high power output requirements of those lasers to
burn those discs. Any burner from the half-point to the end of its life won't be
recording that data as strongly as it should. Eventually it will only work on
specific brands of media then not at all on any of them. Each time the data will
be recorded with less and less depth and resolution.

Make sure the media is as clean from lint and dust as possible during the
recording phase. I knew one person who didn't think twice about putting a lint
covered blank CD or DVD in his burner. And it worked fine for him. The trouble
is the data-pits are recorded almost holographically due to the laser-light. It
might record and verify just fine but later if any of that dust is removed it
can't read those data pits the same way. The read-side of optical media can
contain some defects and dirt later when being read, but don't put anything that
will cause interference patterns in the light-path during the recording process
because they will be recorded into the shape of those data pits. The only way
those discs could be read properly would be to replace all the dust bits on its
surface exactly as they were when recorded.

If you are archiving important photos, always verify after EVERY recording.
Verify again in another CD/DVD reader from another company if possible to ensure
that the data is laid down so that other devices can read it. A burner nearing
the end of its life may not be able to record the data strongly enough for the
average reader to recognize it properly. There are also tons of dye and burner
incompatibility problems since day one, this has never changed. I recently used
a respected brand DVD blank to share something with a neighbor, I used the
better brand so I wouldn't have to make a second trip. I also recorded it on a
brand new DVD burner. Two of their DVD readers from different companies couldn't
read it. I had to go back and try another brand, an inexpensive generic DVD
worked just fine this time on both of their readers.

The only CD's that I ever had fail on me were some MP3 collections that I took
along on an extensive camper trip. With that spindle of CD's bouncing around on
those gravel and rubble roads for months, some of the older 8-year-old brands
lost their reflective coating on top (the most easily damaged layer on any CD in
the past). The aluminized coating literally shattering away from the CD due to
how much vibration and bouncing they were subjected to. Luckily I know how to
fix this by temporarily recreating that reflective layer and backing up the
damaged CD to a new one. Out of a dozen 8-year-old severely damaged CDs I think
I only lost 2 songs. And this was on only a dozen of the 100 or so CDs that I
took with.

.

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