This chapter describes how to use the clustering and locking systems available with GFS, and consists of the following sections:
The Red Hat GFS interchangeable locking/clustering mechanism is made possible by the lock_harness.o kernel module. The GFS kernel module gfs.o connects to one end of the harness, and lock modules connect to the other end. When a GFS file system is created, the lock protocol (or lock module) that it uses is specified. The kernel module for the specified lock protocol must be loaded subsequently to mount the file system. The following lock protocols are available with GFS:
LOCK_GULM — Implements both RLM and SLM and is the recommended choice
LOCK_NOLOCK — Provides no locking and allows GFS to be used as a local file system