The danger of data loss with digital storage.

[h_nu]

My parents have baby pictures of me that are severely color shifted to magenta. There is one that is still approximately correct color but the process was expensive, difficult, and never caught on. It's a GAF print on what appears to be a plastic coated photographic paper.

Maybe I should write down some PGP and Scramdisk passwords. Even if the media survives, my memory may someday fail.

 

[Fluffster]

Backing up data on multiple external drives should provide good defense against data loss. If you have the data on 3 seperate drives I doubt you'd ever lose it (it'd be astronomically rare for 3 drives to faile at the same time).

Your data is still gone if your house burns down.
I keep my digital photographs on my desktop computer and a copy on an external drive. Once a week I synchronize those with an identical setup my father has across town, so we mirror each other's pictures.

I know I should add some kind of WORM medium to the mix, but I know I'm too lazy to keep up with that.

 

[Eugene]

These deterioration can lose some contents, but usually not a complete loss. If a corner of picture or a page of a book gets burned or ripped, that portion is gone, but the rest is good.

If a CD cracks, deforms or suffers from corrosion (air gets under the layer and metal foil gets pitted away, it happens sometimes) and the damage is in the data catalog/index area, ordinary device can not access anything.

Corporations with unlimited funds and the FBI can retrieve the data from such, but the former usually know better than having only one copy, so such recovery is so outrageously expensive it is reserved for forensic evidence.

Thats why I said multiple backups on multiple media formats. You can't really do that with paper. For electronic use CD, Disk, Tape, etc.

 

[Eugene]

DVDs can be a good way to archive data. Using more than one hard drive is good, but DVDs have some advantages. If you drop a hard drive, you will probably lose everything. DVDs can be easily kept at multiple locations. That's what mothers are for, you know.

But to get reliable DVD storage, you have to know how to get good burns, and like always, you need to make more than one. I don't generate much valuable data, so a DVD backup of all important stuff once a month or two is adequate. If last month's DVDs should somehow be lost, I wouldn't lose much by using an earlier one.

To make good DVD burns you need to get good blank DVDs. You can't necessarily tell what media you have by looking at the label. Some media give bad burns, with lots of correctable errors, and some media can make good burns today, but 6 months from now they may be unreadable. These discs may be readable today in your current drive but might not be readable tomorrow, or in a different drive.

To know what discs you have, you need to see the MID (manufacturer's ID) that is recorded on the disc. The CD-DVD speed program (usually called CDspeed) will show you that. People that have thousands of DVDs and are particular about them agree that the MCC MIDs (Mitsubishi Chemical Corp.) and the MIDs used by Taiyo Yuden are the best. Most +R and -R discs sold by Verbatim have a MCC MID. To get Taiyo Yuden you can buy them at rima.com

Then you have to scan the burned disks. Just reading them back is better than nothing, but that just tells you they are readable today in that optical drive. There are tests that can give you more confidence that the disks will be readable in other readers and readable in the future.

The CDspeed program has two tests for this. The Transfer Rate Test can be run on any DVD drive. This test attempts to read the disc at full speed, and plots the speed during the read. Any dips in the graph indicate the drive slowed down because it encountered excessive correctable errors. Well, if your CPU is busy or you have a bad connection to the drive, that will cause dips also.

The Disc Quality test can only be run on drives that can report the number of errors it encounters. The disc is read at a constant speed and the errors per block are shown on a graph. All discs have errors (correctable errors). The difference between a good disc and a bad disc is the number of errors.

You can learn about this and more at cdfreaks.com

One of my tests for important data has always been to place the CD or DVD in another computer and attempt to copy all the data to the drive then open a few at random.
If your stuck with only Microsoft Windows on your burning system then only burn after a reboot and don't do anything else while burning.

 

[Neg2LED]

I don't burn to discs, too danger-prone. if I'm going to use a disc for something i use it within 24 hours of burning...Mostly I use RAIDed hard drives - RAID 5 on the server and most of my computers have RAID 1 on the data drive. I also make it a policy to not keep any file I don't want to lose on a single machine. If I can't afford to lose it, then I duplicate it to multiple machines - usually my desktop, the server and my laptop.

I'm thinking of building a NAS....

--neg

 

[Eugene]

All the RAID'ed drives in world won't protect from a virus, or os issue. Sometimes write once media has its advantages. no one media type is perfect, thats why you backup to multiple types.