System Administration Guide, Volume 1

Consistency Checking of Cached File Systems With the Back File System

To ensure that the cached directories and files are kept up to date, CacheFS periodically checks consistency of files stored in the cache. To check consistency, CacheFS compares the current modification time to the previous modification time. If the modification times are different, all data and attributes for the directory or file are purged from the cache and new data and attributes are retrieved from the back file system.

When a user requests an operation on a directory or file, CacheFS checks if it is time to verify consistency. If it is, CacheFS obtains the modification time from the back file system and performs the comparison.

Consistency Checking on Demand

By specifying the demandconst option of the mount(1M) command, consistency checks can be performed only when you explicitly request them for file systems mounted with this option. After specifying the demandconst option when you mount a file system in a cache, you use the cfsadmin(1M) command with the -s option to request a consistency check. By default, consistency checking is performed file by file as the files are accessed. If no files are accessed, no checks are performed. Use of the demandconst option will avoid the situation where the network is flooded with consistency checks.