NFS Services Administrator's Guide (B.11.31.03) August 2008

4 Configuring and Administering a Cache Filesystem
This chapter introduces the Cache Filesystem (CacheFS) and the CacheFS environment.
It also describes how to configure and administer CacheFS on a system running HP-UX
11i v3.
This chapter addresses the following topics:
• “CacheFS Overview” (page 109)
• “CacheFS Terms” (page 110)
• “How CacheFS Works” (page 110)
• “Features of CacheFS” (page 112)
• “Configuring and Administering CacheFS” (page 114)
• “Using CacheFS” (page 124)
• “Common Problems While Using CacheFS” (page 126)
CacheFS Overview
CacheFS is a general purpose filesystem caching mechanism that improves NFS client
and server performance. CacheFS client performance is improved by caching data to
a faster local filesystem instead of going over the wire to a slow server or on a slow
network. This results in reduced server and network load because the clients send
fewer requests to the server.
In an NFS environment, CacheFS:
• performs local disk caching of filesystems which enables the client systems to
become less reliant on the server
• improves performance of clients on slow networks
• increases the number of clients that can be supported by a single server
• decreases the overall server load which can result in better server performance.
When data is read from a cached NFS-mounted filesystem for the first time, it results
in some overhead when CacheFS writes the data to its local cache. After the data is
written to the cache, read performance for the cached data improves significantly.
CacheFS improves read performance for data that is read more than once. However,
it does not improve NFS write performance. Therefore, good candidates for cached
filesystems include manpages and executable programs, which are read multiple times
though rarely modified.
By default, CacheFS maintains consistency between the cached filesystem and the
remote filesystem, using a consistency checking model similar to that of standard NFS
(polling for changes in file attributes).
CacheFS Overview 109