Name

CacheDirLevels and CacheDirLength

Synopsis

CacheDirLevels number
Default: 3
CacheDirLength number
Default: 1
Server config, virtual host

The proxy module stores its cache with filenames that are a hash of the URL. The filename is split into CacheDirLevels of directory using CacheDirLength characters for each level. This is for efficiency when retrieving the files (a flat structure is very slow on most systems). So, for example:

CacheDirLevels 3
CacheDirLength 2

converts the hash “abcdefghijk” into ab/cd/ef/ghijk. A real hash is actually 22 characters long, each character being one of a possible 64 (2⁶), so that three levels, each with a length of 1, gives 2¹⁸ directories. This number should be tuned to the anticipated number of cache entries (2¹⁸ being roughly a quarter of a million, and therefore good for caches up to several million entries in size).