[pcowans]

Rails running on vanilla Ruby does have particular scaling issues due to the limitations of the Ruby garbage collector. You hit a GC cycle after every 8MB of allocation, which typically takes around 150ms to run, so can dominate the runtime of your requests. We've had 80% of the runtime in GC, even when you include database time.

This isn't necessarily a killer, but it means there's sometimes more work than you might like in scaling. There are patches to tune the garbage collector, and JRuby etc. may help, but ultimately you need to be much more aware of memory allocation than you might think.

[charlesju]

That's an application bottleneck which is fixed by more application servers. This has no effect on scaling what-so-ever.

And by scaling here, we're talking about 1 M to 10 M, not 10,000 to 100,000.