1Global File System 2------------------ 3 4http://sources.redhat.com/cluster/ 5 6GFS is a cluster file system. It allows a cluster of computers to 7simultaneously use a block device that is shared between them (with FC, 8iSCSI, NBD, etc). GFS reads and writes to the block device like a local 9file system, but also uses a lock module to allow the computers coordinate 10their I/O so file system consistency is maintained. One of the nifty 11features of GFS is perfect consistency -- changes made to the file system 12on one machine show up immediately on all other machines in the cluster. 13 14GFS uses interchangable inter-node locking mechanisms. Different lock 15modules can plug into GFS and each file system selects the appropriate 16lock module at mount time. Lock modules include: 17 18 lock_nolock -- allows gfs to be used as a local file system 19 20 lock_dlm -- uses a distributed lock manager (dlm) for inter-node locking 21 The dlm is found at linux/fs/dlm/ 22 23In addition to interfacing with an external locking manager, a gfs lock 24module is responsible for interacting with external cluster management 25systems. Lock_dlm depends on user space cluster management systems found 26at the URL above. 27 28To use gfs as a local file system, no external clustering systems are 29needed, simply: 30 31 $ mkfs -t gfs2 -p lock_nolock -j 1 /dev/block_device 32 $ mount -t gfs2 /dev/block_device /dir 33 34GFS2 is not on-disk compatible with previous versions of GFS. 35 36The following man pages can be found at the URL above: 37 gfs2_fsck to repair a filesystem 38 gfs2_grow to expand a filesystem online 39 gfs2_jadd to add journals to a filesystem online 40 gfs2_tool to manipulate, examine and tune a filesystem 41 gfs2_quota to examine and change quota values in a filesystem 42 mount.gfs2 to help mount(8) mount a filesystem 43 mkfs.gfs2 to make a filesystem 44