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

Consider the following example where the /opt/frame directory is going to be
NFS-mounted from the NFS server nfsserver to the local /opt/cframe directory.
To mount the example NFS filesystem using CacheFS manually, enter the following
command on an NFS client system:
mount -F cachefs -o backfstype=nfs, \
cachedir=/disk2/cache nfsserver:/opt/frame /opt/cframe
The /opt/frame directory can now be accessed like any other mounted filesystem.
When data in /opt/cframe is referenced, it is copied into /disk2/cache.
To mount an NFS filesystem using CacheFS automatically at system boot, add the
following line to the /etc/fstab file:
nfsserver:/opt/frame /opt/cframe cachefs \
backfstype=nfs,cachedir=/disk2/cache 0 0
When data in the /opt/cframe directory is accessed for the first time, the requested
data is retrieved across the network from the NFS server. A copy of this data is then
placed in the local cache directory. All future accesses to the data will be served from
the local cache, assuming the data has not been modified on the server.
When a CacheFS filesystem is mounted, a file or CacheId is created in the cache directory
for it. The name of the file is of the form:
NFS_server:mounted_directory:mount-point
Where each “/” is replaced by “_”. The CacheId is unique for each CacheFS mount-point
and is a link into the part of a cache directory assigned to that mount-point.
For example:
NFSserver : nfss04
Mounted directory : /exp
Mount-point : /mnt
symbolic name : nfss04:_exp:_mnt
Users can explicitly specify the CacheId using the cache ID mount option. If you do
not specify a cache ID, CacheFS constructs one.
Switching Mount Options
CacheFS is commonly used when the data on the server is read a number of times and
rarely modified. For example, consider a filesystem that is initially mounted with the
noconst option. The mount option has been chosen because the data on the server is
rarely modified. If for some reason the data on the server is modified, you may want
to change the mount options. In earlier versions of HP-UX, if you mounted a filesystem
with certain mount options, you could not change those mount options without deleting
or recreating the cache. Starting with HP-UX 11i v3, you can switch mount options
without deleting and recreating the cache.
To change the mount option from noconst to the default option, without deleting or
rebuilding the cache, enter the following commands:
Configuring and Administering CacheFS 115