Using apparently high spec discs is no guarantee of longevity. Mention of what I happen to do, copy 3 yearold backups to new on a rolling basis and keeping in 2 different sites for storage. I also check originals at the same time for any degradation. No mention of writing at reduced speed for archiving purposes. I happpen to always knock down from x52 to 40 for normal burning (slightly larger pits) and then x32 for 3 yearlt archives. French researcher shown cleaning dics radially , not circumferentially. Shame BBC reporter did not mention this factor. Anyone else got any tips ?
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
Yep. I stopped using them. I do my backup to removable HD and usb HD. Much less expensive, and flexible too. Also fine for an image backup of the system disk(and fast restore). I use Paragon(free for private use) and Ghost2003.
Another trick you can use is to apply an additional level of error correction, with e.g. the "dvdisaster" package. You create an ISO image of up to about 85% of the maximum for your chosen disc type, run it through "dvdisaster" to create a set of Reed-Solomon checksums and append them to the ISO, and then burn the resulting enlarged ISO to the medium.
If, when you try to read back files from the disc, you find some sectors unreadable due to damage or deterioration, you can tell dvdisaster to read as much of the disc as it can, and then use the added Reed-Solomon codes to recover the contents of any sectors which weren't readable. The resulting repaired ISO can be burned to a new disc, or (on Linux at least) loopback-mounted to allow files to be retrieved directly.
--
Dave Platt AE6EO
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I have lots of CD-Rs created in 2000, which are unplayable. Expensive audio CD-Rs at that. Stored on a shelf at room temp, boxed, rarely used. also had a few DVDs warp - princo ones mostly, which seem to be two plastic discs stuck together.
forget optical media for archiving. I use external HDD. Also audio tape which has stood test of time.
Depends on what you are backing up and how important it is to you. :-/
I backup on several different *types* of media concurrently. CD/DVD, MO, hard disks and tape. Each medium has different risk issues.
I won't *rely* on a hard disk as a backup medium. It's just too easy for a single spindle failure to cost you a *lot* of data! Even having *two* backups on hard disks doesn't guarantee you are "safe"
[The only time I *almost* lost data was using hard disks as the backup medium. The backups were stored "off line" (i.e., not powered). I went to retrieve something from my "primary" backup -- only to discover the disk *scrambled* (VTOC). I frowned but figured a hard disk failure is something you
*eventually* have to deal with... So, I pulled my *secondary* backup out and spun that up. And it, *too* was scrambled! (I later discovered this was a drive-aggravated bug in the driver so *every* drive of this make/model would end up scrambled!). Thankfully, I had the DRIVES backed up on MO media as well and was able to restore from that -- though it obviously took a bit longer as the MO media wasn't as big as the hard disk]
My current practices are to *push* things that I want to backup onto one of my servers "whenever it is convenient". Then, periodically backup to tape (SDLT), an external USB drive and CD/DVD.
I have maintained some items for more than 20 years using this technique -- though it gets more and more expensive (time) as my archive grows.
Best advice: decide what things you are willing to "lose"; then ask yourself, "If I am willing to lose it, is there any reason why I shouldn't (deliberately!) lose it *now*??"
I have lots of CD-Rs created in 2000, which are unplayable. Expensive audio CD-Rs at that. Stored on a shelf at room temp, boxed, rarely used. also had a few DVDs warp - princo ones mostly, which seem to be two plastic discs stuck together.
forget optical media for archiving. I use external HDD. Also audio tape which has stood test of time.
-B
wwwwwwww
Is there an issue with plastic stored in plastic? I've only used CDrom storage since 2002 . Always stored in plain paper envelopes, no glue , stored vertically and none that I've randomly tried files have had a reading problem
I made a superbackup on a 4GB usb then I found a chkdisk error on it. I had scanned most of my personal documents, including microfilm of all my college notes. I am not too happy with any media. The twenty year old microfilm had started to decay. ANd I am spooked by the IoZip click of death. I have "gold" CDs for my archives.
But a 10MB HD I have in the basement from 1985 still works fine.
*+-I backup on several different *types* of media concurrently.
*+-CD/DVD, MO, hard disks and tape. Each medium has different
*+-risk issues.
Excellent strategy - engineering redundancy.
ON HD: I have a system with batch files which backs up files on the same disc. More often than not, that is what is really needed in case of human error. I also wonder if it is worth saving the ISO of a backup CD or DVD and accessing it via CDanywhere.
ON Tape: I'm surprised to hear this. Back in the 1970s if i played a two year old cassette it had a buzz to it. But that may be some problem caused by the microphones and interference.
Was just browsing a CDR I made in 1999. Have some audio CDR from around then that I listen to on occasion. Odd that your discs didn't last 10 years. I have some that I created with my 1x HP SCSI burner back in the mid 90s that still read fine.
What you have to be wary of is having *some* bad spot on the medium (whatever that is) -- or the *image* of the medium -- causing you to
*lose* the entire contents of the medium! I.e., error codes can't reconstruct "big holes".
The problem with tape is you have to "retension" it periodically in order to avoid print-through. But, with (S)DLT, that's pretty easy to do just in the normal course of *using* it.
On Sun, 30 May 2010 18:51:44 +0100, "N_Cook" put finger to keyboard and composed:
I make it a policy to fill up the entire CD, if only with redundant copies.
For example, let's say you have 100MB of photo files. I'd copy these same files to 7 directories, ie COPY_1, COPY_2, ... COPY_7. That way you have 7 chances to recover your precious snaps in the event of physical damage, CD rot, unreliable burner, unreliable media, etc.
- Franc Zabkar
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What everybody seems to key onto is the useful life of the media,
What might be more of a problem is the useful life of devices to read that media.
Case in point. A friend who runs a small shop called and wanted to transfer her business file to a new computer. The stumbling point was that the media was 5.25 inch floppies. Don't bother criticizing her for being stuck with an obsolete system.
Consider tape backups or even 2.5 inch floppies.
Ten years will those carefully preserved CDs been totally replaced by (fill in the blank with your guess and bet your data on it).
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