larrys@uunet.uu.net (03/09/90)
Periodically someone will ask for the manufacturer's defect list on some old disk drive. What use is that, considering that formatting the disk generates a new defect list? Seems sort of like asking for the shop manual on your Deuce street rod.
jdd@db.toronto.edu (John DiMarco) (03/13/90)
In list.sun-spots you write: >Periodically someone will ask for the manufacturer's defect list on some >old disk drive. What use is that, considering that formatting the disk >generates a new defect list? Seems sort of like asking for the shop >manual on your Deuce street rod. Some defects don't show up at format time. They wait until the most inopportune moment... Disk defects don't usually go away. The set of actual defects on an old disk is a superset of the original set of defects, recorded in the manufacturer's defect list. Every entry in the manufacturer's defect list indicates a definite bad spot on the disk. You don't want to trust format/verify to find them all; a few may be "weak" spots (inconsistently bad). John DiMarco jdd@db.toronto.edu or jdd@db.utoronto.ca University of Toronto, CSRI BITNET: jdd%db.toronto.edu@relay.cs.net (416) 978-8609 UUCP: {uunet!utai,decvax!utcsri}!db!jdd
henry@zoo.toronto.edu (03/14/90)
>Some defects don't show up at format time. They wait until the most >inopportune moment... Disk defects don't usually go away. The set of >actual defects on an old disk is a superset of the original set of >defects, recorded in the manufacturer's defect list. Our experience, with Fujitsu Eagles that have been in production for most of a decade, is quite the opposite: the two lists seem to be almost entirely unrelated. The story we heard, way back when, was that the manufacturer's defect lists on such drives are generated by analog means -- he has no idea how you're going to format the drive -- and say very little about digital results. This was from George Goble, who I am inclined to consider a reliable source. The fix is to run your formatter's diagnostics for *several days* per drive, and map out anything that it hiccups on. That was G.G.'s recommendation, and it worked just fine for us too. I think it's important to distinguish what kind of drive we're talking about. The situation for SCSI drives is probably very different, since there much more of the formatting is the manufacturer's job. I've never worked with those and can't comment on how that affects things.