I recall that the company I was working for had a computer system set up specifically to burn CDs in 1993. Of course it had a CD burner. It also had a special AV hard drive that didn't interrupt the reading of data during thermal recalibration1. On regular hard drives, this operation paused the data flow and therefore the burn would fail, resulting in a bad disc suitable for the garbage. The computer also had no software, other than the operating system and the burning software, that might steal CPU time and slow the flow of data. Burners now have a feature where the writing will be paused while the data flow drops below the rate of it being written to the disc, but back then, as soon as the write buffer emptied, the disc was garbage. So in the old days, once the disc burn started, no one even touched the computer. Just in case.
Oh, did I mention that the blank 650 MB blanks cost in the neighbourhood of $25 each?
So why is it 1993 again? I burned a data disc today that cost me $24 and it took in the neighbourhood of three hours. It wasn't a 650 MB CD, but rather a 100 GB Blu-ray disc. Yes, I know writable CD/DVD/Blu-ray data discs for backup are on their way out. I certainly agree that I won't ever back up my hard drive to writable discs. But in this case, I have my photos backed up to two removable hard drives (one stored off-site) and I'm worried about bit-rot2...which I have experienced. A large capacity optical disc is ideal for this irreplaceable data.
It seems that writable optical discs have undergone some advancement since I last stored any significant amount of data on them.
The obvious advance is capacity. When BD-R discs were introduced, they came in the form of a single-layer 25 GB capacity or a two-layer 50 GB capacity. These days BDXL discs are available in a three-layer 100 GB capacity and a four-layer 128 GB capacity. Given that most years I've taken digital photos have resulted in files that easily fit on a single 25 GB disc, the files are easy to back up. But last year I took photos that total 99.04 GB in size. Sure I could split them across four discs, but that offends my sensibilities, and prevents me from trying these cool higher capacity discs.
The other advance is longevity. M-Disc is a new type of optical disc that uses a non-organic data layer. Regular discs use an organic data later that is subject to chemical changes, especially if the lacquer fails and oxygen comes into contact with the organic material. As a result, these newer discs are more focused on long term storage and claim to last anywhere from a few hundred years to a millennium. Of course that's overkill, even if it's true, but regular discs can fail far more quickly.
I loaded up on 25 GB M-Disc BL-R discs and have backed up all the music I purchased online and I'm starting the process of backing up my photos. I ordered one 100 GB M-Disc BL-R disc for last year's photos. Happily, the burn and verification were successful.
Now I have my photos backed up a fourth time in a non-modifiable form that should take care of things if I find damaged copies on the backup hard drives. All I'll have to make sure of is that I have a working optical drive that can read a BD-R.
- Or did it recalibrate only while idle? I'm not sure. It was 27 hears ago!
- See the Wikipedia entry on the topic.