Correctable errors? That's not how CD-R/DVD-R work…
That is exactly how they work; CDs and DVDs always have an assortment of correctable errors and so do hard drives.
Ohhh, derp, I somehow thought you meant "correctable" in the sense of going back and rewriting a failed sector or something…
(1) I do not remember the details for data CDs but for DVDs, there are two layers of error correction with the second layer catching errors that the first layer missed. Good DVD burners (2) have the capability of doing a surface scan to return the number of errors corrected by the first and second layers of error correction and this reveals the general quality of the burned disk. (3) Only uncorrectable errors show up in the typical media verify function.
CD-ROMs use eight-to-fourteen modulation as one layer of redundancy, the other is the cross-interleaved Reed-Solomon encoding, just like an audio CD. But unlike an audio CD, CD-ROMs also add another layer of Reed-Solomon encoding and a CRC. (That's why a 74-minute blank CD holds 74 minutes of audio, which is actually about 750MB of audio data, will only hold 650MB as a CD-ROM.)
(1) A major reason hard drives have moved to using larger sector sizes is because error correction becomes less efficient as the physical sector length becomes shorter (greater linear density) compared to the defect density. I suspect the same thing was responsible for larger sector sizes in higher density MO disks except where compatibility was required. DVDs had this covered from the start with larger sector sizes and a combination of short and long error correction to handle a much more hostile environment.
Yeah, I remember reading that!
(2) Plextor burners were good for this until they stopped making their own drives.
Yes, it's a pity Plextor and Yamaha stopped making drives — those two were hands-down the best!
ZIP drives depends on an embedded magnetic servo on the disk so the disks are very fragile. Floptical type drives like the LS-120 were much more reliable.
There's nothing about an embedded servo that makes a disk fragile. That's a totally specious argument. Hard disks rely on embedded servo, too, you know — and at tolerances FAR tighter than in a Zip drive.
It is not the embedded servo itself but the embedded servo in combination with the low coercivity of Zip media. This makes it possible to easily erase the magnetic servo with an external magnetic field at which point the disk is trashed because the drive has no way to reformat it.
In theory, yes. But I've literally never heard of that happening. Not once. Remember that even floppy disks aren't nearly as sensitive to magnetic fields as people think, and Zip media would have to have far lower coercivity than those.
I have always wondered if the loss of the embedded servo tracks on Zip media was responsible for damaging the drive leading to the click of death but I avoided them and Jaz drives.
The click of death is a bit of a red herring IMHO, insofar as it actually describes a number of
different failure modes. (And as a computer technician right when these things were popular, I think the failure rate is WILDLY exaggerated.)
In the Zip, one "click" was when misaligned heads caused trouble reading the servo tracks, causing seek attempts that sound clicky. It is not clear to me whether head misalignment was contagious, insofar as I don't know of any way that a bad drive could damage a disk in a way that that disk can damage further drives.
Another Zip "click" was catastrophic head damage, which would cause edge damage to the disk, which in turn would rip the heads off the next drive it was inserted in, damaging the drive and causing it to cause damage to every disk inserted, in a vicious, contagious cycle.
The Jaz was a totally different technology (removable hard disk, same as SyQuest and Orb). Its click of death was basically "standard" hard disk seek errors, plus dust ingress, dust created by shutter wear, etc.
I decided using an embedded servo on soft media was bad idea from the start except for planned obsolescence.
I think that was an unfounded fear. (As for planned obsolescence… I don't really believe in that. IT has more than enough inherent obsolescence, such that adding artificial obsolescence is absolutely unnecessary!)
The old Syquest drives were the same way but with a "hard" magnetic media, damaging the embedded servo was not likely; I never saw it happen but with a flying head, head crashes were always possible.
As I said about Jaz, they sucked in other ways. (FWIW, I saw Jaz drives fail at a rate of probably 10:1 vs Zip. The failure rate on Jaz was absolutely shocking, and I think THAT is what actually led to Zip's undeservedly bad reputation.)
There's no evidence that LS120 is any more or less reliable than Zip, but its far smaller adoption makes it hard to really know its failure rate.
At least when I accidentally wipe an LS120 disk with a magnet, I can reformat it and use it.
For sure, a degaussed Zip can't be reused, but I've never actually heard of it happening. As I said, even floppy disks aren't that sensitive to magnets. It takes an oscillating magnetic field to affect them.
I never used LS120 in any significant way either but only because it never became popular and I was already using 3-1/2 inch MO
MO is something I wish had caught on more, too.
although I think burnable CDs and DVDs are even better for archival and backup purposes because you cannot make a mistake and erase your old data.
True. But the inherent suckiness of media that's written with the same light that reads it (or ambient light, if stored poorly!) makes them questionable in the long run — as experience is showing.
MO disks are the best as far as toughness since they are "hard" magnetic media except during the write process, use optical tracking so the embedded servo data is permanent, and are a non-contact media. Unfortunately optics limit areal density compared to magnetic media.
Yep. At least in MiniDisc, it uses a pregroove, much like CD-R. Data MD is something I REALLY wish Sony had developed further. It was such a convenient format, and MiniDisc media has proven to be spectacularly reliable in the long run. (But the Data MD drives Sony made were much, much, much too slow.)