As it says on the Nginx docs for limit_req

One megabyte zone can keep about 16 thousand 64-byte states or about 8 thousand 128-byte states.


What can a 100m zone for the fastcgi_cache store ?

depending on the length of the fastcgi_cache_key and how many variables that contains i am sure could affect it but be nice to have a example for better understanding of how many file paths are expected to be in the 100mb zone.

http://www.networkflare.com/