we just need to add more Peers and evenly distribute the workload.
> what kind of cache hit rate are you expecting at the peer?
I don't know. We have too many moving parts right now and can't predict anything.
That doesn't make sense! If you add more peers just to keep more files in memory, each peer is serving less and less data. There's a fixed, finite amount of usage that the system will receive, and the more peers you add, the more that usage gets subdivided among the peers. Which means they make less money, which makes the system unprofitable. Moreover, you're spending more money to distribute the file to more peers (well, you're not, you're offloading that to the customer right now), which means the more peers, the more expensive for you or the customer.
The problem you have is that handling more files means cutting peer profits without adding any benefit for yourself or the peers. Storage isn't factored into pricing, which means that any accommodation you make to increase availability (an important part of being a CDN!), the worse the economics end up being.