7 Oct
2007
7 Oct
'07
6:02 a.m.
Jim Leonard wrote:
Ethan Dicks wrote:
Jerome Fine replies:
I noticed the replies by Tim Shoppa and Barry Watzman as well as Ethan
Dicks and Jim Leonard. They were all very helpful.
MANY thanks for everyone who replied. It would seem that my precautions
are at the high end rather than the low end. As for copies, the
Fujifilm DVD-R
spindle of 100 was less than $ 30, so the cost is no longer a factor. I
doubt that
I will use up the spindle at less than a dozen blanks a year before dual
layer media
and drives become standard plus single layer media and drives become more
expensive due to lack of sales. And since the time to collect and
prepare the
files for archive (with their MD5 values) is over an hour and the burn
time per DVD
is only 20 minutes, making an extra copy is very reasonable.
My precautions include producing an MD5 value for each Ghost backup file
which I write to the DVD along with the file name and number of bytes.
Since
each backup file is named CddMMMyy.GHO (dd is the day and yy the year),
the date is also included. After I burn the DVD, I read all the files
to an empty
partition and generate an MD5 value for the new copy which I compare against
the original. In about a week, I will again read the Ghost backup files
When writing DVDs, I always do a read-verify
right after burning, and
for archival data, I tend to create recovery data with programs like
par2, and burn two to three copies. If it's worth my time to archive,
it's worth spending $1 for more than one copy.
This is exactly my procedure as well, but I use QuickPar instead of
par2. I also burn two copies, since high-quality DVD-Rs can be had
for less than $0.50 in bulk. from the DVD
using a READ ONLY DVD drive that I
originally purchased 5 years ago and
use only for that purpose. I don't mind that W98SE requires a reboot
since I have
a faulty hard disk device driver which crashes W98SE after about 5 hours
(also
not a problem since I take a break at least every 4 hours) and I am the
only user.
After I read the files on the DVD for the second time, I will delete the
original.
Then, I suspect that it will be useful to read the December backup for
the last
4 years and re-copy then to a DVD (each are just less than a GB) so that I
have an historical archive.
What are Quickpar and Winrar? Please clarify. If they are similar to
MD5, then
I guess I am already doing the same thing. Actually, I would use FC to
compare
the original and the copy, but I know that FC does not catch all of the
differences
with binary files. Plus, after the original file has been deleted, MD5
is the only
reasonable method I have found of checking the archived file.
My typical process is to use Winrar with a recovery record (parity) of
1%, then take the resulting files and use Quickpar to generate as much
parity as necessary to fill up the DVD-R. I then burn, ***and I make
sure that the DVD-R also has a copy of winrar and quickpar on the
disc*** (just in case 20 years from now someone is trying to extract
my stuff and doesn't know what a *.par file is).
It seems that I have missed a valuable file. Thank you.
The MD5.EXE is not on the DVD, although I do have
the GHOST.EXE file that was used to create the backup
files.
Only Barry commented on dual layer DVD blanks. Has anyone
else had any experience? Are they cost effective as compared
with single layer when the extra capacity is considered.
I have been using the Pioneer 105 drive since 2002 when
my son loaned me his to test everything. The following
year my other son and I shared a new drive for a year
(well he had it 80% of the time and I had it 20%) after
which he decided to buy a faster drive for himself. Prior
to that I had the READ ONLY DVD drive which I still have.
Plus I still have a CD burner from 1997 which also still
works since I have all CD / DVD drives powered off when
not in use.
For those individuals who use a CD to boot foreign OSs,
the Pioneer 105 and the device drivers for W98SE read and
make available to Ersatz-11 the first 16 CD sectors (64 blocks
of 512 characters each is the equivalent for a hard drive)
which I have found to be all zeros for a standard CD.
This allowed me to boot RT-11 from the Pioneer 105 drive
using a raw CD media (as opposed to an actual file on either
the CD or a DVD which Ersatz-11 MOUNTs in the normal fashion)
under Ersatz-11 as opposed to any other CD / DVD IDE based
drive which prevented Ersatz-11 from obtaining access to
the first 16 CD sectors where the boot information for RT-11
(and the file structure for the first RT-11 partition) is
located. I was able to use a SCSI CDROM drive, however,
and Ersatz-11 did manage to see the first 16 sectors on the
media which allowed booting of RT-11 in this case.
For anyone who is interested in creating bootable CD media
for PDP-11 hardware or in emulation under Ersatz-11, I can
probably answer many questions. For SIMH, I haven't any
experience with bootable CD media.
Sincerely yours,
Jerome Fine
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As I said, I lost a file once. That was with
CD-Rs, and that was the
first one out of many hundreds of discs burned (presuming they
verified at write-time in the first place). I _have_ had a number of
discs that didn't verify, and that could be due to a number of causes,
from defective media to "cosmic rays". I have not, however, with that
one previously mentioned exception, lost data (yet?) from disks that
did verify.
Yes, that's been my experience as well. If they're going to be bad,
they're usually bad right out of the gate (ie. didn't pass Verify).
Every year, I take my very first burnt CDR from 1995 out and try to
read it. It has always read. I keep my CDRs and DVDRs in a cool dry
dark place, though; not everyone can store them in optimal conditions.