Originally Posted by
birdstrike
Are you folks saying that if I burn a file to a CD/DVD with a checksum, then read it back, the checksums won't match?
If that were true, no one would ever sell software on CD/DVD.
My home archive is composed of 1) The hard disk image. 2) another hard disk image in a safe deposit box and 3) a stack of DVDs. I trust the DVDs as much as I do the rest of the media.
The optical media is generally very reliable in a static sense. That is to say that as long as you don't need to access it the data is as reliable as most other means. The amount of time for the dye layer to degrade should be long enough that you will have upgraded the backup technology to a newer one by then.
But there are far more ways for an optical disc to be damaged and rendered unreadable than there are for flash or magnetic media, IMO. Chances of "scratching" flash or HDD media are pretty low.
I agree that tape is likely more reliable than optical, but advents in tape technology seem to happen more frequently than optical drives, with the significant potential for leaving old tape media intact but unreadable due to a lack of compatible hardware. My recollection is that LTO reads 2 generations back and writes one generation back. So LTO1 tapes are no good in an LTO4 drive (current model for the past 12-18 months, IIRC). I believe that SDLT is similar. I'm not sure about DDS tapes. Compare that to optical media, where a CD-ROM that you got when they first came out should still be readable today in the most current CD/DVD drive, assuming that the disc isn't damaged or degraded.