JTREWORGY@Wesleyan.BITNET (James Treworgy) (04/11/90)
> In article <9004061744.AA13588@jade.berkeley.edu> C503719@UMCVMB.MISSOURI.EDU ("Baird McIntosh") writes: > [stuff deleted] >>hope that my assessment is incorrect. In any case, I don't think there is a >>way in software to write to a write-protected disk; the hardware won't allow >>this type of write to occur (which is perfectly reasonable and expected). >> > Unfortunately, the write protect mechanism involves an optical detector. If th e > light source is not functioning it is the same as write-enabling the disk. A > defective drive will allow writing to a protected disk. > Proper fail-safe design would have reversed the modes, so that a closed tab > meant write-protect. A failure in that case would mean a default > of write-protect. That's one way to look at it, but if, as you say, the mode had been reversed, your drive would be useless if the mechanism broke down (you wouldn't be able to write to disks). As it is, you are just in a situation where you can't write protect disks if it breaks. I think this has fewer negative effects than not being able to write at all (all the disks I use extensively are write enabled anyway, for obvious reasons). -- James A. Treworgy -- No quote here for insurance reasons -- jtreworgy@eagle.wesleyan.edu jtreworgy%eagle@WESLEYAN.BITNET
jmeissen@oregon.oacis.org (John Meissen) (04/11/90)
In article <9004102044.AA12596@jade.berkeley.edu> JTREWORGY@Wesleyan.BITNET (James Treworgy) writes: >> Proper fail-safe design would have reversed the modes, so that a closed tab >> meant write-protect. A failure in that case would mean a default >> of write-protect. > >That's one way to look at it, but if, as you say, the mode had been reversed, >your drive would be useless if the mechanism broke down (you wouldn't be able >to write to disks). As it is, you are just in a situation where you can't write >protect disks if it breaks. I think this has fewer negative effects than not >being able to write at all (all the disks I use extensively are write enabled >anyway, for obvious reasons). This could be argued many ways. But with the formaer method a failure isn't really catastrophic. Unfortunately with the current situation you have no way of detecting a failure until files start mysteriously disappearing from supposedly write-protected disks. If the mechanism were reversed, as I proposed, then you could still read your data from the disk, allowing you to run in a limited way. As soon as you tried to write to the drive the failure would be evident and you could get it fixed. Assuming you had more than one drive, having one operate in read-only mode temporarily would be safe, not catastrophic.
tomb@hplsla.HP.COM (Tom Bruhns) (04/12/90)
JTREWORGY@Wesleyan.BITNET (James Treworgy) writes: >> In article <9004061744.AA13588@jade.berkeley.edu> C503719@UMCVMB.MISSOURI.EDU >> ("Baird McIntosh") writes: >> [stuff deleted] >>>hope that my assessment is incorrect. In any case, I don't think there is a >>>way in software to write to a write-protected disk; the hardware won't allow >>>this type of write to occur (which is perfectly reasonable and expected). >>> >> Unfortunately, the write protect mechanism involves an optical detector. If th > e >> light source is not functioning it is the same as write-enabling the disk. A Actually, many, if not most or all, 3.5" drives use a microswitch to detect the write0-protect tab. This modifies your arguement slightly, since the switch could stick in either position. Of course, the electronics in an optical sensor could fail in either mode, too; LEDs don't "burn out" like incandescant lamps, so that's not _necessarily_ the predominant failure mechanism. (stuff deleted)