Wikipedia
CacheFS is the name used for several similar software technologies designed to speed up distributed file system file access for networked computers. These technologies all operate in similar ways: they store ( cache) copies of files on secondary memory, typically a local hard disk, so that if a file is accessed again, it can be done locally at much higher speeds than networks typically allow.
CacheFS software is used on several Unix-like operating systems. The original Unix version was developed by Sun Microsystems in 1993. Another version was written for Linux and released in 2003.
Network filesystems are dependent on a network link and a remote server; obtaining a file from such a filesystem can be significantly slower than getting the file locally. For this reason, it can be desirable to cache data from these filesystems on a local disk, thus potentially speeding up future accesses to that data by avoiding the need to go to the network and fetch it again. The software has to check that the remote file has not changed since it was cached, but this is much faster than reading the whole file again.