[TUHS] Disk data layout (was: /dev/drum)

On Monday, 23 April 2018 at 17:30:24 -0600, Grant Taylor via TUHS wrote: This relates to modern disks, of course, where there are different amounts of data on each track. Until about 1990 each track had a constant amount of data on it. "LBA" is newer than the time we're talking of. In those days, disk data was addressed physically, by cylinder, head and sector, terms that only died out round the turn of the century. I was heavily involved in disk data recovery in the 1980s, and I know beyond any doubt that cylinder 0 was on the outside (closest to where the heads retracted before changing a pack). I was amazed when I discovered that CD-ROMs started counting from the inside. But how do I prove it? I've done some net trawling and looking through my pile of junk here, but I can't find anything convincing. http://www.datadoctor.biz/data_recovery_programming_book_chapter2-page16.ht… shows a layout like this, and also the statement The tracks are numbered, starting from 0, starting at the outside of the platter and increasing as you go in. But by itself that's not overly convincing. I looked at the manual for the IBM 3330, but I couldn't find anything specific. Does anybody else have any useful reference? Of course, you can map CHS to LBA in multiple ways, and conceivably it has been done differently. Greg -- Sent from my desktop computer. Finger grog(a)lemis.com for PGP public key. See complete headers for address and phone numbers. This message is digitally signed. If your Microsoft mail program reports problems, please read http://lemis.com/broken-MUA