You have enabled passivation. By doing so this store will only be written to when an entry is evicted. In this case you have set the max-entries to 5000000, so you will have to write ~5000000 + 1 entries before you see something written to the cache store.
There is more information on passivation here 
Got that, thank you
FYI - the max-entries parameter you set was for the filestore not the eviction policy. Since you do not have an eviction policy, you would probably never see anything written to the cache store because you would run out of memory if you keep adding entries to the cache. If you set an eviction policy with 500K max-entries then you would see data being written to the filestore at 500k+1 entries.