The first characteristic of a mount point determines which type of fileset is named in the mount point. A read-only or backup fileset has a .readonly or .backup extension; a read/write fileset has no extension.
When a mount point names a fileset with a .readonly or .backup extension, the Cache Manager uses only the specified version of the fileset. The Cache Manager never accesses the read/write version of a fileset when it encounters a mount point that names a read-only or backup version; if the explicitly named version is unavailable, the Cache Manager reports an error. However, depending on the mount point type, the Cache Manager can access the read-only version of a fileset when it encounters a mount point that names the read/write version (the fileset name with no extension).