General Multiserver question for larger installations

[webguyz]

Was wondering if larger installations break up their servers by function (separate mail server, db, web servers) or just keep adding servers as needed with complete set of functions where each new server has web, mail, db, etc. and have all clients functions on only that one machine.

I can see advantages both ways and was wondering what others n the real world found most effective.

Thanks!

[till]

In most larger installations, servers are separated by function. E.g. like this:

1 Controlpanel Server
X Mailservers
X Webservers
X DB Servers
2 DNS servers

Regarding the database servers I prefer in most caeses to have the db servers on the web servers as db connections over a local socket are faster then db connections over a external network, so the setup can be also:

1 Controlpanel Server
X Mailservers
X Web + Database servers
2 DNS servers

[webguyz]

Till,

Those were my thoughts as well, but then I started thinking about redundancy. If you put all mail/web/db services for clients on one server, and that server goes down, all the other servers that have a similar setup are still up and fewer people are affected. if you have a dedicated mail server or DB server and it goes down, you are affecting a larger number of people.

The downside would be more services to maintain on more machines.

Thanks!

[till]

ISPConfig 3 supports splitting of servers as well as mirroring, so you can have e.g. 2 mail servers were one server mirrors the configuration of the other server to get a redundant server or balance the load.

[webguyz]

When you say mirroring your talking about clustering, correct? For some reason I was thinking that was setup as a master/slave in the reading I've been doing. Not sure what you mean then about load balancing. That sounds exactly what I'm looking for.

Thanks!

[till]

The clusters etup is a mirror setup that syncs the same configuration on as many servers as youlike. You can use this setup for failover or run aloadbalancer in front of it.