Why UNIX I/O is so slow (was VAX vs SUN 4 performance)

[Doug Gwyn]

In article <441 at mn-at1.k.mn.org> alan at mn-at1.UUCP (0000-Alan Klietz) writes:
-Berkeley should start over.  The whole business with "cylinder groups"
-tries to keep sets of blocks relatively near each other.  With the new
-disks today, the average SEEK TIME IS OFTEN FASTER THAN THE ROTATIONAL
-DELAY.  You don't want to keep blocks "near" each other, instead you want
-to make each extent as large as possible.  Sorry, but cylinder groups are
-archaic.

Such considerations should lead to the conclusion that each type of
filesystem may need its own access algorithms (perhaps in an I/O
processor).  This is easy to arrange via the File System Switch.