floppy media failure

[Jules Richardson]

Al Kossow wrote:
>  > I suppose in an ideal world I'd assume that catastrophic failure of 
> the media
>  > could happen very quickly - so priority is to get a snapshot of the 
> disk onto
>  > modern storage before that happens.
> 
> The failure mode I've seen is oxide/binder coming off, clogging the head 
> and carving little concentric rings in the media :-(

Yes, that's the one. I've not seen it often, but when it does the end result's 
not pretty. I had one drive a while back where the upper head got ripped clean 
out of the drive when the coating on the disk let go.

> Once the buildup starts, S/N ratio goes into the toilet, so the inner 
> tracks often have errors.

Soon as I hear that squeaking sound of heads scraping against things that 
they're not supposed to, I stop reading - I just didn't get to the drive 
mentioned above fast enough :-(

> One of the techniques I've thought about to mitigate this is, as you 
> say, just
> snapshot all of the data without analysis, to avoid sitting on a track 
> for a
> minimal number of rotations, stagger-read tracks, or read them in inner 
> to outer track order.

Good thinking. I wonder if the surface order matters too - thinking about it, 
it seems like the majority of failures I've seen have been on the upper 
surface. Possibly something to do with the spring loading arrangement in a 
typical drive (I'm talking 5.25" here - I don't think I've seen a 3.5" disk 
fail in the same way, and I don't normally touch 8" drives*)

* I've got a pair of Shugart 801's sitting in the garage awaiting cleaning, so 
that will change...

Hmm, I wonder if blowing compressed air at the heads when reading would help, 
or whether the coating on the disks is sufficiently "sticky" that it'd still 
fix itself to the head no matter what?

> There doesn't seem to be any obvious visual indication that the binder 
> will strip
> off a disc, oddly enough. You'd think there would be something like 
> physical discoloration when this was likely to happen.

I'd noticed that too. Some brands seem to be more prone than others - not 
enough to form a useful pattern, but it seems that given a box of disks from 
random manufacturers, if one fails then others from the same manufacturer in 
that box will fail too. (but disks from the same manufacturer that have been 
stored in different conditions may well be fine)

It's irritating. IMHO all the more reason to get everything possible onto 
modern storage first, and worry about how to get it *back* onto original media 
again at a later date :-)

cheers

Jules