[Zope] Tweaking Zope DB- and connection parameters

[Germer, Carsten]

Hello everyone,

I'm trying to figure out what I can set all (I know) Zope Parameters to
to get a good overall performance on our "old" live installation.
We have a new System with upgraded Zope and the like in the making but
untill then I'm trying to keep what is up smooth and stable.

Machine: Dual Pentium with 4Gig Ram running on Suse Linux. Zope 2.7.2
with Python 2.3.4 and ZMS for the Sites. There's a recent Apache 1.3.x
in Front for caching and like 25 Sites running on the system, some very
rarely visited some more loaded.

While running the system with out-of-the-box-parameters at times of high
load the RAM went full, the machine started swapping and spiraling down
so I started to set limits in Apache and Zope. I was mostly just
guessing!

Apache is set to "MaxClients 50"
Zope.conf has set "zserver-threads 5" and 
<zodb_db main>
    cache-size 500
    pool-size 25
...
</zodb_db>

With this settings the machine tops at load around 1.8 - 2 and no
swapping takes place *puuh* but still users sometimes, too often for
users taste, get to wait a minute and longer for their page. For me it
tastes like a garbage collection or whatnot because after 5-20 minutes
everything is fine again for an hour or two...

- Apaches "MaxClients" is set for general limit
- zserver-threads: How many ppl, approx., can connect with this set to
5? Would be good to synchronize this with the apache settings somehow?
- cache-size: This is per DB connection (pool-size) as I have learned, I
did set this down to limit memory usage
- pool-size: number of concurrent DB-Connections as I learned. Does
every concurrent connection have to have it's own db-connection or do N
zserver-threads share one?

What I'm looking for is general advice how these parameters work and can
be set for best cooperation. Or if there are other Params that I have
missed yet ;)

E.g. "every zserver-thread uses one db-connection and can server one
user so for 50 concurrent users you have to set everything to 50 and
tweak cache-size according to 'Cache Parameters' in the Zope config and
your RAM-load behaves" Which is nonsense I bet but something like that
would help me great time.

Thanks in Advance for any Help! /Carsten

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Carsten Germer         Deutsches Elektronen Synchrotron (Web-Office, IT)
phone:  +49-40-8998-1661                                    Notkestr. 85
web: http://wof.desy.de                                    22607 Hamburg
e-mail: carsten.germer at desy.de                                   Germany
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