Apache Reference: mod_proxy, CacheDirLevels

CacheDirLevels

Maximum Subdirectories Depth for the Proxy Document Cache
Syntax: CacheDirLevels A
Example: CacheDirLevels 2
Since: Apache 1.1

This directive sets the number of subdirectory levels in the proxy cache directory. Cached data will be saved this many directory levels below CacheRoot.