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Date:      Wed, 03 Nov 1999 11:06:33 -0700
From:      Chris Fedde <cfedde@fedde.littleton.co.us>
To:        Jonathon McKitrick <jcm@dogma.freebsd-uk.eu.org>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: swap space... 
Message-ID:  <199911031806.LAA98299@fedde.littleton.co.us>
In-Reply-To: Your message of "Wed, 03 Nov 1999 14:27:31 GMT." <Pine.BSF.4.02A.9911031426490.67462-100000@dogma.freebsd-uk.eu.org> 

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Jonathon McKitrick writes:
 +---------------
 | So TOO much swap space can be a bad thing?  I just saw a comment saying
 | too much space will allow the OS to swap everything to disk and reduce
 | performance.
 | 
 | -jonathon
 +---------------

Too much swap allocated wastes disk space that could be used for
something else.  But there are valid reasons why you might want to
configure lots of swap.  One is that you are using the mfs for /tmp
and want to store big files there.  If swap is large then big files
and old files will tend to be in the backing store rather than in
memory.

You will not generally have a performance hit from just allocating too
much swap.  And using to much swap is also not always an indication of a
problem ether.  The big indicator is the 'page out rate' and the 'scan rate'
reported by vmstat(8).  These indicate how often memory pages are moved to
backing store and dirty pages are cleaned for re-use.

chris
__
Chris Fedde	  <cfedde@fedde.littleton.co.us>
303 773 9134


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