[imp] Server Farms..

[Andrew Morgan]

On Wed, 31 Mar 2004, Michael Bellears wrote:

> > > I have a couple of questions regarding the "real" webservers setup:
> > >
> > > 1. We currently run MySQL for IMP prefs/vpopmail users/spamassassin
> > > prefs etc - Is it advisable to have each "real" server run it's own
> > > MySQL - And have each in a master/slave setup?
> >
> > We have MySQL running on a separate server.  This keeps the
> > webmail servers really simple to configure.  We do not use
> > MySQL replication.
>
> Ok - What impact does this MySQL server dieing on you have?
>
> I want to eliminate all(If possible!) single points of failure - Hence
> the reason for the MySQL master/slave setup.

Obviously, if the MySQL server goes down, so does all of Webmail!  :)

For us, that's not a big concern.  We're using a Dell 2650, which has
decent built-in redundancy, so we are far more likely to commit some human
error that takes it down than any sort of hardware failure.  To become
fully redundant on the backend as well would require a second server,
obviously, which would probably also have to be hosted behind the load
balancer.  For us, it's just not worth the expense or the hassle.

> > > 3. What about logfiles - We would have all users mail etc on an NFS
> > > share - Can you do the same for logfiles?(Or do you get locking
> > > issues?)
> > > - From a statistical aspect, it would be a pain to have to combine
> > > each "real" servers logfiles, then run analysis. Also from
> > a support
> > > perspective - How are support personnel supposed to know
> > which "real"
> > > server a client would actually be connecting to in order to see if
> > > they are entering a wrong username/pass etc?
> >
> > Most of the useful information about a user's problem are in
> > the Horde syslogs, which we send to a central loghost.  You
> > could let syslog combine the logs from all your webmail
> > servers, or use a merge script to do it after the fact.
> > Syslog includes the name of the originating machine, so you
> > know which real server is involved.
> >
> > Apache logs stay local on each webmail server, but we've
> > rarely needed to look at them to diagnose problems.
>
> My major concern will be the qmail logs - multilog cannot(?) log to an
> external host....I will have to ask about this on the qmail list.

We use a smart relay mail host, so all the outbound mail from the webmail
servers goes to our campus mail relays for processing.  We have an
outbound only config for postfix on each of the webmail servers, with
postfix logging to the central loghost.  My recommendation would be to
*not* queue mail on the webmail servers for outbound deliver.  Hand it off
to a dedicated box.

	Andy