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3. filesystems
4. ocfs2.txt

OCFS2 filesystem
==================
OCFS2 is a general purpose extent based shared disk cluster file
system with many similarities to ext3. It supports 64 bit inode
numbers, and has automatically extending metadata groups which may
also make it attractive for non-clustered use.

You'll want to install the ocfs2-tools package in order to at least
get "mount.ocfs2" and "ocfs2_hb_ctl".

Project web page:    http://ocfs2.wiki.kernel.org
Tools git tree:      https://github.com/markfasheh/ocfs2-tools
OCFS2 mailing lists: http://oss.oracle.com/projects/ocfs2/mailman/

All code copyright 2005 Oracle except when otherwise noted.

CREDITS:
Lots of code taken from ext3 and other projects.

Authors in alphabetical order:
Joel Becker   <joel.becker@oracle.com>
Zach Brown    <zach.brown@oracle.com>
Mark Fasheh   <mfasheh@suse.com>
Kurt Hackel   <kurt.hackel@oracle.com>
Tao Ma        <tao.ma@oracle.com>
Sunil Mushran <sunil.mushran@oracle.com>
Manish Singh  <manish.singh@oracle.com>
Tiger Yang    <tiger.yang@oracle.com>

Caveats
=======
Features which OCFS2 does not support yet:
	- Directory change notification (F_NOTIFY)
	- Distributed Caching (F_SETLEASE/F_GETLEASE/break_lease)

Mount options
=============

OCFS2 supports the following mount options:
(*) == default

barrier=1		This enables/disables barriers. barrier=0 disables it,
			barrier=1 enables it.
errors=remount-ro(*)	Remount the filesystem read-only on an error.
errors=panic		Panic and halt the machine if an error occurs.
intr		(*)	Allow signals to interrupt cluster operations.
nointr			Do not allow signals to interrupt cluster
			operations.
noatime			Do not update access time.
relatime(*)		Update atime if the previous atime is older than
			mtime or ctime
strictatime		Always update atime, but the minimum update interval
			is specified by atime_quantum.
atime_quantum=60(*)	OCFS2 will not update atime unless this number
			of seconds has passed since the last update.
			Set to zero to always update atime. This option need
			work with strictatime.
data=ordered	(*)	All data are forced directly out to the main file
			system prior to its metadata being committed to the
			journal.
data=writeback		Data ordering is not preserved, data may be written
			into the main file system after its metadata has been
			committed to the journal.
preferred_slot=0(*)	During mount, try to use this filesystem slot first. If
			it is in use by another node, the first empty one found
			will be chosen. Invalid values will be ignored.
commit=nrsec	(*)	Ocfs2 can be told to sync all its data and metadata
			every 'nrsec' seconds. The default value is 5 seconds.
			This means that if you lose your power, you will lose
			as much as the latest 5 seconds of work (your
			filesystem will not be damaged though, thanks to the
			journaling).  This default value (or any low value)
			will hurt performance, but it's good for data-safety.
			Setting it to 0 will have the same effect as leaving
			it at the default (5 seconds).
			Setting it to very large values will improve
			performance.
localalloc=8(*)		Allows custom localalloc size in MB. If the value is too
			large, the fs will silently revert it to the default.
localflocks		This disables cluster aware flock.
inode64			Indicates that Ocfs2 is allowed to create inodes at
			any location in the filesystem, including those which
			will result in inode numbers occupying more than 32
			bits of significance.
user_xattr	(*)	Enables Extended User Attributes.
nouser_xattr		Disables Extended User Attributes.
acl			Enables POSIX Access Control Lists support.
noacl		(*)	Disables POSIX Access Control Lists support.
resv_level=2	(*)	Set how aggressive allocation reservations will be.
			Valid values are between 0 (reservations off) to 8
			(maximum space for reservations).
dir_resv_level=	(*)	By default, directory reservations will scale with file
			reservations - users should rarely need to change this
			value. If allocation reservations are turned off, this
			option will have no effect.
coherency=full  (*)	Disallow concurrent O_DIRECT writes, cluster inode
			lock will be taken to force other nodes drop cache,
			therefore full cluster coherency is guaranteed even
			for O_DIRECT writes.
coherency=buffered	Allow concurrent O_DIRECT writes without EX lock among
			nodes, which gains high performance at risk of getting
			stale data on other nodes.
journal_async_commit	Commit block can be written to disk without waiting
			for descriptor blocks. If enabled older kernels cannot
			mount the device. This will enable 'journal_checksum'
			internally.