Multiple partitions on 1 and 2 Unix PC hard disks.

[andrew.d.hay]

In article <1990Nov16.033801.978 at shibaya.lonestar.org>, afc at shibaya.lonestar.org (Augustine Cano) writes:
> In preparation for a 2 stage upgrade, I now seek some net advice.
[]
> Cons: 
[]
>       3 - having / and /u on the same disk would make for lots of head
>           movement.  However, would this be any worse than the standard,
>           one-partition per drive, unix pc way of doing things?

somewhat.  with one partition, you have
|---FILES---|-----FREESPACE-----|
with two, it's
|files|freespace|files|freespace|
thus involving (slightly) longer seeks.
however, see comment on thrashing below.

[]
> Another possibility is to have /tmp as the other partition on
> the second drive.  This would speed things up, but somehow I feel that a
> 40 Mb /tmp is excessive.  How big should /tmp be, if it gets its own
> partition?  I have stuffed some pretty big things in /tmp before and it was
> nice to have all the free space on the drive available, so maybe the speed
> penalty of having /tmp in the / partition is worth it.  Comments?

i don't think /tmp should be larger than 16M; probably 8 would be enough.

> Also, I seem to recall that without re-linking the kernel, you
> can only have 2 partitions per drive (in addition to /dev/fp000 and
> /dev/fp001), is this correct?  Does this also apply to the second drive,
> without a swap partition?  Also, would it do any good to have a swap
> partition larger than 5000 blocks?  (I also plan to add 1.5 Mb RAM to a
> RAM-less combo board.)

you can have up to 16 partitions per drive (including swap and boot), but the
kernel mount table is only 4 entries long.  THIS INCLUDES THE FLOPPY!

if you run a lot of programs at once (or big ones), there is a benefit in a
larger swap space.  when swap is full, the next process to swap out gets
dropped on the floor.

[]
> Opinions anyone?  Those of you who have 2 HDs and/or multiple partitions,
> how did you do it?  Any other considerations I have overlooked?  Have any
> benchmarks been run on different partitioning schemes and what directories
> were placed where?  Will some programs be broken by the multiple partitions?
> Which ones?

we have a lot of 2-drive unix machines here.  they're partitioned thusly:
/ and users (/u on the 3b1) on drive 1, and /usr and /tmp on drive 2.

one goal: make root a static filesystem; remove all directories that thrash to
mounted filesystems.
another goal: balance filesystem activity across both drives.

one program that will break is install software; it uses mv to shift files
out of /tmp.
of course, mv could be fixed (on my list of things-to-do) to work across
filesystems...

-- 
Andrew Hay		+------------------------------------------------------+
Ragged Individualist	| 	You just have _N_O idea!  It's the difference    |
AT&T-BL Ward Hill MA	|	between _S_H_O_O_T_I_N_G a bullet and _T_H_R_O_W_I_N_G it!     |
a.d.hay at att.com		+------------------------------------------------------+