So for those wondering what I've done with the wiki upgrade, I've made a
simple diagram. As we get more hardware and resources you can see where
we're headed as far as HA goes in our environment. I'm still trying to
acquire a NAS or SAN for us, this will make what we need to do much
easier. Also at the application layer once we get in a Xen environment
we can add and remove app servers easily without having to expand the
number of proxy servers we have until they get overloaded. I'm still
experimenting with various things but right now app2 is our biggest
SPOF[1] as it houses the wiki and shares it with app1. The proxy
servers are using mod-rewrite [P] to proxy services. Basically the load
balancer balances between proxy[1-2] and each proxy in turn proxies to
app[1-2]. Instead of proxy1 -> app1, proxy2 -> app2. The proxy servers
will also mount or contain copies of static content (like /extras, or
favicon.ico)
There are many tweaks to be made to make this useful and hands-off HA,
but this is a good first step for us. As always I'm interested in
discussion so send it my way.
-Mike
[1] Our load balancer may also be a SPOF, not sure.