What is the best Ruby on Rails setup to handle a site with low to medium traffic? Why?

WIth your requirement, I also suggest that you start using heroku (http://www.heroku.com) free stack to see if it fit your needs (maybe it will, unless you plan to upgrade) I also suggest that you get familiar with Passenger (it's an Apache module built for RoR), this will help you a lot in the future. MySQL will suffice for your database as the traffic is relatively low, unless you want to write humongous SQL statements, there should be no problem at all The advantage of Heroku is that it will take care of the server setup and deployment script for you. Once you reach a certain level and is confident in you deployment skill, you can switch to an empty VPS on Amazon EC2 if you really like to customize your web server EngineYard ... well they change a lot and break my stuffs too frequently to consider

I second those answers. We (http://barrelrun.com) use Engineyard just because it allows for more flexibility (you get full ssh access to a "real" server), Heroku is easier to use AND has a free tier (EY does not) but you can't customize your server (in fact, you don't even get a server).  I found it hard to give up on that :-) If you really want to RYO, you can't go wrong with Amazon's EC2 (which is basically what EY sits on-top off).  They also offer a free tier (for 1 year at least I believe) and I have seen white-papers that claim the free tier can easily support millions of page hits/month.  In this case I would go with: NGINX with Passenger -> much easier to manage and lighter than Apache, WEBrick is really only for development and I also have not used Mongrel outside of a dev instance so can't comment on it's use in a production instance. MySQL -> why not?  It's free, works really nice with Rails and gives you everything you could ever want from an RDBMS (disclaimer, I work at Oracle but I used MySQL long before we acquired it).  You are also right not to jump on the NoSQL bandwagon, it is a very specialized tool for a very specialized requirement, one which you probably will never have to use You gonna need a deploy tool (capistrano) and I also highly recommend a tool that helps bootstrapping your environment (Chef) I would really only resort to the RYO solution if you are a masochist that wants to learn all this stuff (I did!) otherwise, stick to the PaaS providers.

I feel you should definitely try to set it up once on a bare bone system. It might be a little difficult because your coming from windows but if your looking for a horizontally scaling structure then a load balancer + apache + unicorn + mysqldb is all you need. Capistrano to make releases automated and deterministic :) ... Do remember that on a bare bone box you'll have to install all the basic services as well. A great resource is this one: http://articles.slicehost.com/2009/10/15/capistrano-series-installing-apache-with-passenger-mod_rails-support Search around on all the slicehost articles on how to install all of the above. Mostly its very simple yum and apt-get commands. The big gotcha will be getting stuck for a long time on something like an apache configuration. This WILL happen and there's really no way through it except by doing it. Or a unicorn setting you didn't know about. I actually know a very big site that gets 3M hits per day using above arch on 12 different boxes. Mostly a read only site though. The second time around you'll be able to get a bare bone box up in under 1hr from scratch. And you'll be a unix guru. If however you are doing a startup and u don't have any income, then I highly recommend heroku because market risk is bigger than execution risk.

Definitely go with heroku. You get total sclability, and zero server and sysadmin costs. Heroku is actually free -- it lets you save the salary of a sysadmin. We are currently having more than 8 million unique users a month, with 2-3 million PV/day, and I don't even know what server we are running on. And I couldn't care less. It works, it scales, and I can deploy with a git push. So we are focusing on what matters -- feature development.

Definitely start with Heroku's free tier to see if it works for your requirements. Then move to their paid tier till you get big / complicated. If you get to a point where Heroku becomes too expensive or it's not customizable enough, then you can think about the next step. But, IMHO, not for now.

I absolutely agree with Mattias Petter Johansson that you should dispense with setting all of that stuff up yourself and just use Heroku. We have used it successfully with clients who have hundreds of thousands of users. We have also used Engine Yard for many years, but they are a bit less reliable.

http://engineyard.com is good, although relatively expensive.  They sit on top of AWS and share deep roots in Ruby on Rails