We are looking to host some 50-100 rails apps. What would be the best server model to handle this? By server model, I mean like several load balanced servers or small VPS per site etc.
I've used "mod_rails" and a good estimate is that each site is going to run at around 100mb of memory.
Any suggestions would be greatly appreciated.
As much as I'm a virtualisation junkie, if these Rails apps are all in the one "management domain" (ie you're responsible for keeping them all running, you're not hosting them for all manner of different developers who need to do their own thing now and then) I think that a single physical machine will work best. You'll probably be able to run all the sites on the one machine, if it's big beefy one and they're all really lightly loaded sites.
Going the VPS route involves a fairly sizeable overhead for running a single 100MB process each, as well as the disk space and hassle factor of having 50-100 extra copies of your OS running (and needing to be patched, managed, etc) -- even with solid automation (which I highly recommend regardless of your situation) it's going to be significantly more work to manage 100 machines than 1.
On the other hand, if you're hosting 50-100 random Rails apps, from different developers, who will be doing some of the system management themselves, then VPSes start to look a lot more useful.
Set up several virtual private servers with decent allocations or perhaps a few dedicated servers and spread them out, but don't overcomplicate yourself unless you really have to.
The advantage of using a quality VPS is that you will have the advantage of access to many cores, redundant HDDs with good I/O, as opposed to a dedicated server which may come in more expensive to set up with a RAID-10, a decent quad core and sufficient memory.
