I know Chuck Guzis has written about this, but I don't see that he's done so publicly in the last few years, so I thought I'd ask here about his and others' views on the perennial question of whether (some) 3.5" DSHD disks can be reliably used in DSDD-only drives. The oft-repeated claim is that writing can appear to work just fine, but that even a few months later read errors will occur.
On <http://www.retrotechnology.com/herbs_stuff/guzis.html> Chuck was quoted as (actually, correct me if I'm wrong -- it's a little hard to be sure this was Chuck's words) as saying "Usually, they're just fine, with the error rate approximately the same, whether or not 2D or HD media was used." Just before that, he said "I think that the overall quality of DSHD 3.5" media isn't what it used to be, so that might contribute to the general impression that 3.5" HD diskettes used as 2D aren't reliable. I have problems enough finding reliable 3.5" DSHD floppies used as such." Chuck et al., what's your feeling now, both on the overall reliability of HD disks in DD drives, and on whether it depends on how recently the disks were produced? Elsewhere on the page (I don't recall now if it was Herb or Chuck that said it) it was conjectured that HD disks that have never been formatted as HD, -OR- disks that have gone through a good degaussing, will have better luck retaining data. What does everyone think about this? And would an electromagnetic library security system (the kind that's like a tube through which checked-out materials are put; often with a caution not to put tapes or floppies through it) be a suitable degausser? -- Eric Christopherson
