Over the last 3 years I have been in the process of building a network of sites using wpmu initially and now wp multisite. Last month's bot attack was a eye opener for me on the risk of using multisite as it left my 300+ network dead in the water for several days.
I have gone through the process of hardening my installations security by adding security plugins among other changes but this left my server way under powered.
I was already using Multi-DB and a CDN so I decided it was time to move the DB to it's own server, which was relatively painless however my application server is still under powered so I am looking to move my install to a new server.
So, in the interest of not having to go through this process again in short order I wanted to get more info on the best server setup/config for a growing network. Google didn't reveal anything exciting so I am hoping someone at WPMuDev can reveal some secrets.
Is it just a bigger more powerful server that I need or do specific OS work better than others for Multisite.
Let's say I am projecting 500-1000 moderately busy sites what is the best config for this: server, OS, plugins. The more details you can provide the better.