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Date:      Tue, 02 May 2000 22:00:45 +0100
From:      Peter McGarvey <Peter.McGarvey@telinco.net>
To:        FREEBSD-Questions <freebsd-questions@freebsd.org>
Subject:   BSD Theology: swap, /var, /tmp and /usr/tmp
Message-ID:  <390F41FD.5880279E@telinco.net>

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Theological problem this.  Facts and Opinions welcome...

Okay, I /think/ I know what I'm doing when I slice-up a disk for a
FreeBSD system...

	/ -> 64MB
	swap -> 2 * memory (rounded-up to the nearest MB)
	/usr -> the remaining disk

Once setup I link /var and /tmp to /usr/var and /usr/temp

This is the way I've always done it, I'm quite happy doing it this way,
it works for me and I've never had any problems.

Fine, but now some upstart has asked me to set up a FreeBSD system with
the following....

	/ -> 5MB
	swap 1 -> 512MB (equal to memory)
	swap 2 -> 512MB 
	/var -> 2GB
	/tmp -> 2GB
	/usr -> remaining disk

My first instinct is that the guy is barking mad (he is a Linux groupie
so... (and Linux does have a nasty habit of apropriating every entry in
the partition table))

However I've hit a snag - when it comes to FreeBSD partitions and slices
I know the HOW (and there is lot's of help on that), but I'm not too
sure of the WHY (and help here is lacking).

1. What I need is some rational reasoning why the way I do 
   things is right/wrong. 

2. Why the way Linux man wants it is right/wrong.

3. Some info on the optimal size of swap

4. Where's the best place to put /var and /tmp

Here is what I was told...

On the issue of the 2 swap I was told two swap partitions were needed as
"we may need to turn one off as too much swap will slow the machine
down".  

Furthermore, I was told the 2*memory rule is no longer valid "once the
physical memory has exceeded 64MB"  Can this true?  Have I needlessly
been waisting mt HDD space by making swap too big?

My thoughts were that swap was used as needed, when needed, and that
pages are not swapped to disk on a whim just because the swap space
existed (or perhaps this is how linux works so he's assuming FreeBSD
does it this way too).

As for /var and /tmp why not link them to /usr/var and /usr/tmp.  I can
understand putting them on physically seperate devices.  But is it
strictly necissary to put them in their own slice?  Is there a
performance benefit?  or a is there some extra resiliency?

Whilst I'm at it what is the difference between /tmp and /usr/tmp.  I've
always treated them a seperate entities - assuming linking /tmp to
/usr/tmp was a bad thing.  Linux man maligned FreeBSD big time when he
found there were two temporary directories.  I couldn't respond as I
didn't know - and I refused to descent to his level by insulting his
prefered OS.

Like I said this is mainly a theological problem.  so all Facts and
Opinions welcome...


-- 
TTFN, FNORD

Peter McGarvey, Unix Administrator
Network Operations Center, Telinco Limited


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