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Documentation / filesystems / gfs2.txt

Based on kernel version 2.6.26. Page generated on 2008-07-16 21:12 EST.

1	Global File System
2	------------------
3	
4	http://sources.redhat.com/cluster/
5	
6	GFS is a cluster file system. It allows a cluster of computers to
7	simultaneously use a block device that is shared between them (with FC,
8	iSCSI, NBD, etc).  GFS reads and writes to the block device like a local
9	file system, but also uses a lock module to allow the computers coordinate
10	their I/O so file system consistency is maintained.  One of the nifty
11	features of GFS is perfect consistency -- changes made to the file system
12	on one machine show up immediately on all other machines in the cluster.
13	
14	GFS uses interchangable inter-node locking mechanisms.  Different lock
15	modules can plug into GFS and each file system selects the appropriate
16	lock 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	
23	In addition to interfacing with an external locking manager, a gfs lock
24	module is responsible for interacting with external cluster management
25	systems.  Lock_dlm depends on user space cluster management systems found
26	at the URL above.
27	
28	To use gfs as a local file system, no external clustering systems are
29	needed, simply:
30	
31	  $ mkfs -t gfs2 -p lock_nolock -j 1 /dev/block_device
32	  $ mount -t gfs2 /dev/block_device /dir
33	
34	GFS2 is not on-disk compatible with previous versions of GFS.
35	
36	The 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
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