Global File System ------------------ http://sources.redhat.com/cluster/ GFS is a cluster file system. It allows a cluster of computers to simultaneously use a block device that is shared between them (with FC, iSCSI, NBD, etc). GFS reads and writes to the block device like a local file system, but also uses a lock module to allow the computers coordinate their I/O so file system consistency is maintained. One of the nifty features of GFS is perfect consistency -- changes made to the file system on one machine show up immediately on all other machines in the cluster. GFS uses interchangable inter-node locking mechanisms. Different lock modules can plug into GFS and each file system selects the appropriate lock module at mount time. Lock modules include: lock_nolock -- allows gfs to be used as a local file system lock_dlm -- uses a distributed lock manager (dlm) for inter-node locking The dlm is found at linux/fs/dlm/ In addition to interfacing with an external locking manager, a gfs lock module is responsible for interacting with external cluster management systems. Lock_dlm depends on user space cluster management systems found at the URL above. To use gfs as a local file system, no external clustering systems are needed, simply: $ mkfs -t gfs2 -p lock_nolock -j 1 /dev/block_device $ mount -t gfs2 /dev/block_device /dir GFS2 is not on-disk compatible with previous versions of GFS. The following man pages can be found at the URL above: gfs2_mkfs to make a filesystem gfs2_fsck to repair a filesystem gfs2_grow to expand a filesystem online gfs2_jadd to add journals to a filesystem online gfs2_tool to manipulate, examine and tune a filesystem gfs2_quota to examine and change quota values in a filesystem mount.gfs2 to find mount options