How do you determine what physical device a file in on?

[der Mouse]

In article <1991Jun25.174729.11481 at StarConn.com>, dror at StarConn.com (Dror Matalon) writes:

> I suspect that there are only machine dependent ways.  Given two
> files x and y. I want to determine if they're on the same PHYSICAL
> devie.

Right you are: it's machine-dependent at best and impossible at worst.
(Suppose it's NFS-mounted from wuarchive.wustl.edu; how do you tell
whether they've got that tree on multiple drives?)

For that matter, either or both of the files may be on more than one
physical device.  As a simple example, consider disk striping, which
causes some pieces of the file to be on one device and other pieces on
others; for another, consider disk mirroring, which causes the file to
be entirely present on multiple devices.

For that matter, how do you define a physical device?  Disk drive?
Disk spindle?  Disk platter?  Disk surface?  Disk track?

Or the file may be on a RAMdisk, which arguably comes close to not
being on any physical device.

Why do you care whether they're on the same physical device?

					der Mouse

			old: mcgill-vision!mouse
			new: mouse at larry.mcrcim.mcgill.edu