The cache size indicates the partition size. Cache size should always be lesser than the cache capacity as it is the maximum size to which the cache can grow. The sum of all the partition sizes must be less than or equal to the cache size.
The amount of disk space available for the proxy cache has a considerable effect on cache performance. If the cache is too small, the Cache GC must remove cached documents to make room on the disk more often, and documents must be retrieved from content servers more often; therefore slowing performance.
Large cache sizes are best because the more cached documents, the less the network traffic load and the faster the response time the proxy provides. Also, the GC removes cached documents if users no longer need them. Barring any file system limitations, cache size can never be too large; the excess space simply remains unused.
You can also have the cache split on multiple disk partitions.
Changing the cache structure is time-consuming.