I'm running option 2). 2 active/active load balanced postfix servers with a 
seperate policyd on each. The backend is a load balanced MySQL cluster with 2 
active/passive mysql nodes and 2 active/active data nodes. I've not seen any 
performance issues at all and we deliver approx. 150K messages a day across the 
two servers.

If you need any more info on our setup feel free to ask.

Thanks
Ian

-----Original Message-----
From: [email protected] [mailto:[email protected]] 
On Behalf Of Simon Hobson
Sent: 12 December 2011 16:14
To: [email protected]
Subject: Re: [policyd-users] Multiple servers

[email protected] wrote:
>We are looking at setting up a cluster of outbound mail servers using 
>policyd, and I was wondering what the configuration of the mysql 
>database would look like.  Is the database supposed to be independent 
>for each node that is serving mail, or is it possible to have all of 
>the mail servers pointed to the same database, sharing the cumulative logging 
>for policies?
>The only policy we plan on implementing is a limit on how many messages 
>a SASL user can send per hour.

You have a number of options. You don't really want a separate database per 
node as you'll just end up with out of sync data and a general nightmare.

So your options are (AFAIK) :

1) Run one policy server (and backing database) and call if from each mail 
server. This is what I've done for a small cluster - and the shared DB is also 
used with Postfix Admin. This is what I'd suggest as the load is actually 
fairly low, even for a busy server.

2) Run a shared backend database, but a separate policy server on each mail 
server.

3) Run a separate policy server on each mail machine, AND a separate database 
(replicated) for each server.

TBH, I can't see any point in 3 - just a complication too far. Option
2 may have some merit, but probably limited performance advantage.

Of course, if you want resilience then you could run a replicated pair of 
backend databases, with a policy server each, and split your mail servers 
between the policy servers. Or various other permutations.


FWIW, when I was having some performance issues (eventually tracked down to a 
bug in the version of <something> I was running, I found that my limiting 
factor was Postfix - it seems to be limited to about
2 queries/s to the policy server from each thread. I did some tests and found I 
could easily load up the single policy server with multiple streams of queries 
and it would chew through them at something like (IIRC) 60/s even on my fairly 
low spec machine running multiple guests under Xen.

--
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed author 
Gladys Hobson. Novels - poetry - short stories - ideal as Christmas stocking 
fillers. Some available as e-books.
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