Should I host multiple Plone sites in a single Zope instance?

Question

I’ve got a Plone site in development, and that will soon migrate to a production server, but I’m about to start work on another project in Plone. I know I could create more than one Plone site in the Zope instance (for example by following instructions linked to from an existing question), but is that the best way to host these once launched?

Is there a benefit in having each site run in a different Zope? It seems to me that the buildout configuration might get complex otherwise.

Are there downsides to one-site-per-Zope? I can already see that the resource needs might go up rather a lot.

Answer 1

We always deploy a new Zope instance per site. Websites always change, and if you deployed multiple sites per instance, you have the following downsides:

• All the sites must follow the same software releases. You cannot upgrade a component for one site only.
• Software updates cause downtime for all sites hosted in the same instance.
• If one of the sites becomes disproportionally more popular, it'll dominate the various caches, to the detriment of the other sites. They will become disproportionally slower as their data has to be fetched from disk, always.
• You cannot simply scale up one site to meet demands without having to scale up the other sites too. Want to go from one instance to two? You'll not only need to add a load balancer, you need to add a load balancer configured to handle all the sites.

Unless you are hosting a series of totally uniform websites that have to move along in lock-step, there are really no upsides to hosting multiple sites in an instance.