In the event that your server is unavailable, visitors should still be able to access your site because CloudFlare serves the visitor a page from its cache.
CloudFlare’s global CDN has 12 edge nodes around the world. Our CDN automatically caches your static files at our edge nodes so these files are stored closer to your visitors while delivering your dynamic content directly from your web server. CloudFlare then uses a technology called Anycast to route your visitors to the nearest data center. The result is that your website, on average, loads twice as fast for your visitors regardless of where they are located.