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[mailto:[EMAIL PROTECTED]] On Behalf Of
Sent: Thursday, January 23, 2003 3:41 PM
Subject: NMBCLUSTERS and Kernel config


Im getting ready to go with our FreeBSD production mail server and Ive
been reading that to optimize network mbufs, specify the NMBCLUSTERS
options in the kernel.  Ive read that setting this to a quarter of your
physical RAM on this is the way to go, or devising a number from a
mathematical equation based upon your maximum number of connections at
peak (meaning, 800 connections at peak equals an NMBCLUSTER of 25600, or
mathimatical breakdown 800 connections X 32K per session = 25600KB)

Does anyone have a good way to devise a number for this, or is it really
even needed?  Ive a GB of memory in a Compaq DL320.  The FreeBSD
handbook says typically this is set to 1024 - 4096, adding to my
confusion of what I need to set this to, if anything.

Thanks in advance for any insight,


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i guess i can't give much more insight, other to say this: i've setup a
mail server under freebsd, and changed the kern.ipc.nmbclusters option
to 32768. If you do a 'man tuning', it can explain a little better,
though i suppose you've already done this (it suggests between 4096 and
32768 for machines with greater amounts of memory, which is why i chose
32768). i've got 4 gigs of ram in this machine, so you're mileage may

my netstat -m output:
knappster@eeyore:~> netstat -m
258/720/131072 mbufs in use (current/peak/max):
        258 mbufs allocated to data
256/680/32768 mbuf clusters in use (current/peak/max)
1540 Kbytes allocated to network (1% of mb_map in use)
0 requests for memory denied
0 requests for memory delayed
0 calls to protocol drain routines


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