Need recommendations on how to select partitions

[Carl Rigney]

With two 900GB disks I'd like to put root on a 8-16MB partition on 0a,
/tmp on a 16-32MB partition on 1a, /usr on 0d and /usr/local on 1d, and
split swap evenly between 0b and 1b; 2x memory size on each.  The
advantage of this is that in an emergency if you lose your first disk you
can overwrite /tmp and /usr/local with root & /usr and boot from the
second disk.  It can also be very handy when doing upgrades to be able to
"test" the upgrade on the "spare" partitions before overwriting your old
OS.  I also like to put /var on its own partition, and then put the
remainder of the two disks into /home/foo/1 and home/foo/2 where foo is
the name of the machine.  Leave lots of room on /usr for it to expand in
future OS releases.

With this scheme we only need to back up /usr once, since we never change
it after our initial installation; all local programs go into /usr/local,
and nothing goes into the root filesystem unless it absolutely has to; we
keep a list of all changed files in /CHANGES so upgrades are very quick -
no playing "hunt the non-standard file."

A possible disadvantage to just making it two big disks without partitions
is that files may get scattered further across the disk, reducing
performance.  Also, for drives that use Zone Bit Recording the outer
cylinders can be read faster than the inner ones, and that's where root
swap and tmp go.  Another consideration is time for fsck'ing the disks on
a reboot; SunOS fsck's root and /usr before giving you the single user
shell; its much faster if these are < 100MB instead of a full GB.
(Everything gets fsck'ed when you go multi-user, but frequently when
troubleshooting or installing you do a lot of single-user rebooting.

Carl Rigney
cdr at amd.com
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