What kind of server is recommended for Plone?
When setting up Plone, what kind of server is recommended?
The first thing to remember is that Plone is not an "I just want to host my weblog" or "I simply need a web forum" or "I need a wiki" kind of product. It is a powerful (but easy-to-use and extend) system which demands quite a lot from the server. It's more like an operating system than an application, to use an analogy. Therefore, if you are just looking to solve a simple problem, there are probably less demanding and better suited applications out there.
Plone is heavier on RAM and CPU usage than your run-off-the-mill web system. It's built to do a lot of different things, and should preferably be hosted on a dedicated server if possible.
The most important consideration when building a Plone server is to have enough RAM. The more RAM you have, the more Plone can hold in memory, and the faster it will be. For a straightforward Plone site (such as a small- or medium-sized department intranet for a company), 200-300MB of memory will do. For a large, complex site with heavy traffic (such as plone.org), you'll want more, perhaps as much as 1-2GB of RAM.
It's also helpful to have fast processor. Again, a smaller site could use a 1-2GHz machine, but for larger sites, it's helpful to have a multi-processor, high-speed machine.
Also remember that the way Plone ships by default, it's not set up for deployment, but for development and flexibility. Before you let your site go live, you should read up on caching and optimization. The out-of-the-box Plone installation is set for ease-of-development, not speed. Typically, you'll use CacheFu, along with a proxy, like Apache or Squid. With minimal effort, a Plone site can go 10-40x faster (or more) than the out-of-the-box settings.
Plone has a technology, ZEO, which allows you to operate several Plone servers (either on different physical machines, or several servers on the same machine) so that they can use the same database. With a load-balancer in front, this is an excellent way to scale your site and build availability.
Plone will run excellently on all modern operating systems: Windows, Linux, OS X, and other Unix variants. Most people run Plone on Linux, so will probably hear the most talk about this, but, rest assured, there are plenty of people running Plone on your operating system, whatever that is.