Question about disk cylinders (and some humour)

cocobongo

There was a brief explanation about cylinders in one of the lessons on hard drives types. It's still not clear to me what they are, but I suspect this isn't really used manually in most cases.
At a later lecture one of the lab exercises uses this command fdisk -C 130 imagefile so I went to the man pages to learn about the -C flag and the documentation hilariously confirms my suspicions:

-C, --cylinders number
Specify the number of cylinders of the disk. I have no idea why anybody would want to do so.

So, I have to ask: is (or was) familiarizing with this low-level concepts something commonly seen in the real world?

Thank you.

coop

This is one of those things which is almost always obsolete (but believe it or not, some hardware and/or software still looks at or uses it) but vestiges of it can still be required for backwards compatibility and software that still thinks it matters. you don't have cylinders in SSDs and even most rotational media has built in software that obscures the actual physical layout, but I can remember having to specify the cylinders on some distros in cases my brain has obscured.