I’m currently working on getting my JRuby on Rails app live. I’ve got a
host with 512 MB memory. I assumed this would be enough (especially
this is not going to be a high-traffic website–it’s something I’m just
building myself for fun and as a little research project). Originally I
tried using Tomcat, but was getting some weird exceptions when system
commands were run via the backtick (`). It was suggested to me to try
Glassfish so I’ve installed that, and gotten it working. I saw this
 from Albert today discussing the memory needed for a JRuby on Rails
running on Glassfish–and he’s saying 2 GB isn’t enough. Now I don’t
if that much is needed because of a high volume of web site traffic or
specific requirements of his app, but there’s no way I’m going to
a 2 GB VPS package.
So this got me thinking: what are the memory requirements of the various
deployment options? I’m thinking that Tomcat has a much lighter memory
footprint than Glassfish. What about other options? Should I consider
Keep in mind that of the 512 MB, I need to reserve a sizeable chunk (128
MB+) to run Lilypond  since my web app uses it to generate sheet
Plus I need enough to run Apache, MySQL, etc.
My hosting provider allows me to add 64 MB of memory for an extra
up to 768 MB if need be, but I’d like to fit in the 512 MB if possible.