I’ve been running some tests for the past few days of how Grails performs under load on a limited memory server - actually a virtual server. Running tomcat with a max heap of 128M (-Xmx128M) and requested lots of pages using 10 simulated clients. I was pleasantly surpised, grails performed well under these conditions.
You can see more about this at http://grails.org/Deployment
and http://grails.org/Grails+Test+On+Virtual+Server