what are recommended numbers of "directory levels" for cache

[squid-list]

Hi,

are there some recommendations on the numbers of "Level-1" and
"Level-2" numbers for caches depending on their sizes? e.g, if the
cache size is:

* 10 Gb -- recommended Level-1= ? Level-2= ?
* 20 Gb -- recommended Level-1= ? Level-2= ?
* 30 Gb -- recommended Level-1= ? Level-2= ?

Thanks. :)