How do disks work, on UNIX mostly, as well as in general?<P>

A disk sector (or block) is 512 contiguous bytes, as well as a header and 
trailer with error checking information, on one side of a disk platter 
under one head.
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A track is the entire length of the path that a disk head traces over one 
side of a disk platter.  A track is made up of multiple sectors.
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A cylinder is the collection of tracks on multiple platters on a single 
position of the heads.
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On Solaris, disk slices are groups of cylinders which are used by a file 
system.
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On Solaris, disk slices have two flags - w or r (writable vs. read-only) 
and m or u (mountable, like a normal file system, or unmountable like swap 
or backup).
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