Cache File System

The Cache File System (CacheFS) is a general purpose file system caching mechanism that improves server performance and scalability by reducing server and network load.

CacheFS performs local disk caching of remote Network File System (NFS)-served file systems. Clients, especially on slow links such as PPP, notice an increase in performance because local disk access is faster than remote file system access. Reduced access requests to the server increases the server's performance and allows more clients to access the server.

However, CacheFS performance improvements are dependent on the type of file system access. It suits file systems where data is read more than once. It has no impact on write performance or if data is read only once.

Summary of Change

What’s New for Customers Migrating from HP-UX 11i v1 September 2005?

Introduces a new command, cachefspack, that packs files and file systems in the cache. It also sets up and maintains files in the cache.
Introduces a new mount option, weakconst, that verifies the cache consistency with the NFS's client copy of file attributes and delays committing of changes to the server.
Provides full implementation of the demandconst option.
Provides support for changing mount options without deleting the cache.
Provides support for error messages to be printed to standard error instead of standard output.
Provides improved error messages that now contain the command name.
Provides support for 64-byte long file names.

What’s New for Customers Migrating from HP-UX 11i v2 June 2006?

See “What’s New for Customers Migrating from HP-UX 11i v1 September 2005?”

Impact

A new command, cachefspack, packs files and file systems in the cache. The cachefspack command also sets up and maintains files in the cache. New features include long file name support. The new mount option weakconst, when used instead of the default option, results in improved response times of CacheFS.

Note that CacheFS does not support NFSv4.

Compatibility

CacheFS on HP-UX 11i v3 is changed from the previous versions as follows:

cfsadmin -s directory prints an error message and returns a non-zero value when run on an invalid directory, non-existing mount point, or a cachefs mountpoint not mounted with demandconst option. In earlier releases, it returned 0.
To improve mount command performance, fsck is no longer executed automatically. This means that if a cache in the cache directory is deleted using cfsadmin -d cache_ID cache_directory, fsck must now be run explicitly on the cache directory before attempting to mount a cached file system using this cache directory. If fsck is not run, the mount fails with the following error message:
mount -F cachefs: mount failed No space left on device

Performance

There is improvement in the time taken to mount a CacheFS file system using a cache directory with a lot of cached data.

Documentation

For further information, see the following manpages:
- mount_cachefs(1M), cfsadmin(1M), cachefsstat(1M), cachefspack(1M), umount_cachefs(1M), fsck_cachefs(1M), packingrules(4M)
Also see the following documents, available at http://docs.hp.com/en/netcom.html#NFS%20Services:
- ONC+ Release Notes
- NFS Services Administrator’s Guide

Obsolescence

Not applicable.