[Setup] Multiple sites - horizontal scaling options?

[scw]

Hi All,

I have a large number of sites to support within one Zope instance,
and am wondering about best practices for development in this case.
I've used most of the advice in Professional Plone Development in
designing two products (site.policy & site.theme) , but it seems like
the buildout method is primarily focused around the one Zope, one
Plone site configuration.

I'm interested to hear if any other folks have tackled similar setup
challenges, and what approaches they've taken.  I'd love to keep all
my customizations for each site on disk if possible. I could
potentially run multiple Zope instances, but am worried about the
performance and management aspects of this option.

cheers,
Shaun