OT CD-R Life Expectancy

This may be of interest to those of using CD's for backups:

CD Dye Info

Plus a post here on the topic:

UK Independent Article

I guess most folk were aware of the need to treat CD's with some care, but I didn't realise that the cheapest CD's have dyes which may only last a few years.

As far as my PLC programs go, a full hardcopy printout, along with a CD, always goes in the file. This came in handy a few years ago when we lost the CPU on a GE series 3. The tape had erros on it, and I ended up using the printout to manually correct the errors in the program once it was loaded on the new CPU.

As far as mew stuff goes, we backup the job folder onto both a CD-RW, and a backup Hard Drive. For the last 4 years, I've been replacing the backup hard driive by coping the the contents on to a new Backup Hard drive, then placing the old backup in a fire proof safe. I do this once a year. I expect most of my PLC based jobs to have a max life expectency of about 40 years. I figure by the time our backup data is lost, it'll be somebody else's problem, as I dont intend to stay here that long.

Many of my CDs have been around a while. I haven't had any go bad, yet EXCEPT for the Verbatim brand. Those oxidized within a few months! I won't touch them even now that they've changed the design.

Here's a tip: when you pick a CD, make sure the foil layer doesn't go all the way out to the edge. I don't think those Verbatim CDs were properly sealed.

Now DVDs, on the other hand... One little scratch and that sucker is TOAST!

AK

I agree with the hardcopy archival. The hardcopy comes in handy for those quick troubleshooting calls. I use two CD backups plus a project file on a server that gets backed up every day. This gives me five total backups.

I had a CD-RW go bad on me once, lost a lot of data I had on it...Other than that over the years, I have had no issues. I'd be curious to know how long data lasts on a HDD???


Greg

I've taken to backing up my current project on CD-RWs because it'too big for floppies. I recently had the CD-RW fail after I had used it for an absolute maximum of 100 copies, although the life is generally quoted as being several thousand writes.

I suspect the problem might have to do with the fact that I was usually saving the file under the same name (the older copy was being saved under it's date name on the server, so I never lost any data, I was only using the CD-RW as a transport medium between PC and PLC). I'm not sure how the whole business functions, but I could imagine, that because I was always using the same name, the FAT table was constantly getting rewritten in the same area. The multiple thousand write lifetime is certainly based on randomly distributed writing.

The other problem, with read failures on older drives I've experienced already on the replacement CD-RW in under 20 writes under the same name - I've now taken to a new naming scheme for my transport files!!!

I always had problem with CDRW. This is not just limited to one PC either, usually with restoring data or adding new data. I still use CDR though since they are so inexpensive.

However, my experiences with DVD+RW is very positive so far. Maybe DVD+RW standard is a more mature one.

OT: The EZautomation CD catalog/demo I received last week had a "separated layer" and was DOA. The very first dead CDR I ever seen.

Just discovered that even with using different names on the current CD-RW, after less than ten writes I'm again unable to read some files on the CD. The CD-RW is from Imation (who I believe are the largest manufacturer), so maybe my old CD drive is in the process of giving up the ghost!

Onsite we allways use EPROMs (or Flashcards as it is today).

Home we have backup on the server. This in turn has its own backup scheme - handled by the IT department. I trust that I can retrieve a backup from there even in the extreme future.

I dont trust CDs or DVDs in general. The national library in Denmark states that regular CDs that are more than 10 years old start to show errors. And you can count on that their CDs are kept under optimal conditions. It is not all CDs that have erors but the tendency is clear and increasing. Only use writable CD and DVD media as temporary storage !

In addition to the server backup, I have a small portable HD that I have stored ALL my projects. Handy for getting project data no matter when you are home or abroad. And it is ridiculesly cheap. Much cheaper than storing on CDs or DVDs. And faster. And easier.

A couple of portable HDs could be an acceptable backup system for a small business without an IT-department to ensure server backup.

edit: By the way, you have all probably seen the shops advertising "kits" for converting VCR tapes to DVDs. I hope their customers will not be angry in 5-10 years time when they want to see that precious movie from the marriage or the graduation or something else they feel important.

In addition to the server backup, I have a small portable HD that I have stored ALL my projects.

Click to expand...

What drive are you using for this, Jesper?

Fortunately, I'm only using the CD-RW as a Transport medium so it's not a big problem, but I'm certainly now aware of the problem which I certainly wasn't before (not so acutely, anyway).

Anybody any idea how secure MMCs are for long term storage?

Always assuming you stay well within the number of rewrite limits, this might be another convenient way to keep back-ups. Even hard-disks have only a limited life nowadays, in some cases only a couple of years under normal use (which of course a pure Backup disk wouldn't be getting).

I just started using a LaCie 80GB external HD that I got from CDW (one of the few places my company allows purchases from) for under $95. It has USB and I can get all my plc programs and my entire desktop on there without problem. Also for plc backups, we write the program to a server that is backed up weekly and I keep a local copy of the program at the plc on a 16MB thumb drive attached to the front of the plc. I've had a few problems with the CDs losing data, but my storage system consists of a stack of CDs without covers laying on my desk.

I also use a LaCie USB drive. Its the small model that gets powered off the USB link - no clunky external power supply.

I notice that many more suppliers come out with USB disks (the type without external power supply) right now.

(its amazing how many USB gizmos that I have assembled in a relatively short time: DVD drive, Floppy drive, Flashcard reader, PC-to-PC link cable, Hard drive, Flash memory "stick", camera, mouse, serial adapter - the pile is geting bigger everytime I look).

I have taken to using either TDK or Kodak gold CDR disks. Alledgedly the gold coating lasts a lot longer, costs more too. You only get what you pay for.

2 copies of everything by the way.