Actually, the cache's "BSD reserved 10%" is not a red herring, even
though it is true that the cache manager runs in the kernel. For, even
though the CM is running in the kernel, when it is executing a system
call (e.g. write) for a non-root user, it is constrained by the 10%
reservation scheme.
Lyle is right, however, that the CM doesn't consider space used by
CacheItems, VolumeItems or various inodes or indirect blocks, and so
traditionally, on top of the BSD 10%, it is a good idea to leave a
little more space available.
