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Currently, the default behavior of O_DIRECT writes was allowing
concurrent writing among nodes to the same file, with no cluster
coherency guaranteed (no EX lock held). This can leave stale data in
the cache for buffered reads on other nodes.
The new mount option introduce a chance to choose two different
behaviors for O_DIRECT writes:
* coherency=full, as the default value, will disallow
concurrent O_DIRECT writes by taking
EX locks.
* 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.
Signed-off-by: Tristan Ye <tristan.ye@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
97 lines
4.0 KiB
Plaintext
97 lines
4.0 KiB
Plaintext
OCFS2 filesystem
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==================
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OCFS2 is a general purpose extent based shared disk cluster file
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system with many similarities to ext3. It supports 64 bit inode
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numbers, and has automatically extending metadata groups which may
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also make it attractive for non-clustered use.
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You'll want to install the ocfs2-tools package in order to at least
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get "mount.ocfs2" and "ocfs2_hb_ctl".
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Project web page: http://oss.oracle.com/projects/ocfs2
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Tools web page: http://oss.oracle.com/projects/ocfs2-tools
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OCFS2 mailing lists: http://oss.oracle.com/projects/ocfs2/mailman/
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All code copyright 2005 Oracle except when otherwise noted.
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CREDITS:
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Lots of code taken from ext3 and other projects.
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Authors in alphabetical order:
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Joel Becker <joel.becker@oracle.com>
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Zach Brown <zach.brown@oracle.com>
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Mark Fasheh <mfasheh@suse.com>
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Kurt Hackel <kurt.hackel@oracle.com>
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Tao Ma <tao.ma@oracle.com>
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Sunil Mushran <sunil.mushran@oracle.com>
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Manish Singh <manish.singh@oracle.com>
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Tiger Yang <tiger.yang@oracle.com>
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Caveats
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=======
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Features which OCFS2 does not support yet:
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- Directory change notification (F_NOTIFY)
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- Distributed Caching (F_SETLEASE/F_GETLEASE/break_lease)
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Mount options
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=============
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OCFS2 supports the following mount options:
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(*) == default
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barrier=1 This enables/disables barriers. barrier=0 disables it,
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barrier=1 enables it.
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errors=remount-ro(*) Remount the filesystem read-only on an error.
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errors=panic Panic and halt the machine if an error occurs.
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intr (*) Allow signals to interrupt cluster operations.
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nointr Do not allow signals to interrupt cluster
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operations.
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atime_quantum=60(*) OCFS2 will not update atime unless this number
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of seconds has passed since the last update.
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Set to zero to always update atime.
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data=ordered (*) All data are forced directly out to the main file
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system prior to its metadata being committed to the
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journal.
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data=writeback Data ordering is not preserved, data may be written
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into the main file system after its metadata has been
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committed to the journal.
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preferred_slot=0(*) During mount, try to use this filesystem slot first. If
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it is in use by another node, the first empty one found
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will be chosen. Invalid values will be ignored.
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commit=nrsec (*) Ocfs2 can be told to sync all its data and metadata
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every 'nrsec' seconds. The default value is 5 seconds.
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This means that if you lose your power, you will lose
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as much as the latest 5 seconds of work (your
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filesystem will not be damaged though, thanks to the
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journaling). This default value (or any low value)
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will hurt performance, but it's good for data-safety.
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Setting it to 0 will have the same effect as leaving
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it at the default (5 seconds).
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Setting it to very large values will improve
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performance.
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localalloc=8(*) Allows custom localalloc size in MB. If the value is too
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large, the fs will silently revert it to the default.
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localflocks This disables cluster aware flock.
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inode64 Indicates that Ocfs2 is allowed to create inodes at
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any location in the filesystem, including those which
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will result in inode numbers occupying more than 32
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bits of significance.
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user_xattr (*) Enables Extended User Attributes.
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nouser_xattr Disables Extended User Attributes.
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acl Enables POSIX Access Control Lists support.
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noacl (*) Disables POSIX Access Control Lists support.
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resv_level=2 (*) Set how agressive allocation reservations will be.
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Valid values are between 0 (reservations off) to 8
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(maximum space for reservations).
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dir_resv_level= (*) By default, directory reservations will scale with file
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reservations - users should rarely need to change this
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value. If allocation reservations are turned off, this
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option will have no effect.
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coherency=full (*) Disallow concurrent O_DIRECT writes, cluster inode
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lock will be taken to force other nodes drop cache,
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therefore full cluster coherency is guaranteed even
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for O_DIRECT writes.
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coherency=buffered Allow concurrent O_DIRECT writes without EX lock among
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nodes, which gains high performance at risk of getting
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stale data on other nodes.
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