Currently cache partitions are 8GB. Because each has a write pointer, this means on a decent size
disk there are a hundred or more write pointers which means a lot of seeking for writes
(which really should be aggregated). The proposal is to make it possible to have large partitions
(up to .5 PB) by increasing the side of the cache directory entry from 8 to 10 bytes and using the
additional bits for the offset.