1OCFS2 filesystem
   3OCFS2 is a general purpose extent based shared disk cluster file
   4system with many similarities to ext3. It supports 64 bit inode
   5numbers, and has automatically extending metadata groups which may
   6also make it attractive for non-clustered use.
   8You'll want to install the ocfs2-tools package in order to at least
   9get "mount.ocfs2" and "ocfs2_hb_ctl".
  11Project web page:
  12Tools web page:
  13OCFS2 mailing lists:
  15All code copyright 2005 Oracle except when otherwise noted.
  18Lots of code taken from ext3 and other projects.
  20Authors in alphabetical order:
  21Joel Becker   <>
  22Zach Brown    <>
  23Mark Fasheh   <>
  24Kurt Hackel   <>
  25Tao Ma        <>
  26Sunil Mushran <>
  27Manish Singh  <>
  28Tiger Yang    <>
  32Features which OCFS2 does not support yet:
  33        - Directory change notification (F_NOTIFY)
  34        - Distributed Caching (F_SETLEASE/F_GETLEASE/break_lease)
  36Mount options
  39OCFS2 supports the following mount options:
  40(*) == default
  42barrier=1               This enables/disables barriers. barrier=0 disables it,
  43                        barrier=1 enables it.
  44errors=remount-ro(*)    Remount the filesystem read-only on an error.
  45errors=panic            Panic and halt the machine if an error occurs.
  46intr            (*)     Allow signals to interrupt cluster operations.
  47nointr                  Do not allow signals to interrupt cluster
  48                        operations.
  49noatime                 Do not update access time.
  50relatime(*)             Update atime if the previous atime is older than
  51                        mtime or ctime
  52strictatime             Always update atime, but the minimum update interval
  53                        is specified by atime_quantum.
  54atime_quantum=60(*)     OCFS2 will not update atime unless this number
  55                        of seconds has passed since the last update.
  56                        Set to zero to always update atime. This option need
  57                        work with strictatime.
  58data=ordered    (*)     All data are forced directly out to the main file
  59                        system prior to its metadata being committed to the
  60                        journal.
  61data=writeback          Data ordering is not preserved, data may be written
  62                        into the main file system after its metadata has been
  63                        committed to the journal.
  64preferred_slot=0(*)     During mount, try to use this filesystem slot first. If
  65                        it is in use by another node, the first empty one found
  66                        will be chosen. Invalid values will be ignored.
  67commit=nrsec    (*)     Ocfs2 can be told to sync all its data and metadata
  68                        every 'nrsec' seconds. The default value is 5 seconds.
  69                        This means that if you lose your power, you will lose
  70                        as much as the latest 5 seconds of work (your
  71                        filesystem will not be damaged though, thanks to the
  72                        journaling).  This default value (or any low value)
  73                        will hurt performance, but it's good for data-safety.
  74                        Setting it to 0 will have the same effect as leaving
  75                        it at the default (5 seconds).
  76                        Setting it to very large values will improve
  77                        performance.
  78localalloc=8(*)         Allows custom localalloc size in MB. If the value is too
  79                        large, the fs will silently revert it to the default.
  80localflocks             This disables cluster aware flock.
  81inode64                 Indicates that Ocfs2 is allowed to create inodes at
  82                        any location in the filesystem, including those which
  83                        will result in inode numbers occupying more than 32
  84                        bits of significance.
  85user_xattr      (*)     Enables Extended User Attributes.
  86nouser_xattr            Disables Extended User Attributes.
  87acl                     Enables POSIX Access Control Lists support.
  88noacl           (*)     Disables POSIX Access Control Lists support.
  89resv_level=2    (*)     Set how aggressive allocation reservations will be.
  90                        Valid values are between 0 (reservations off) to 8
  91                        (maximum space for reservations).
  92dir_resv_level= (*)     By default, directory reservations will scale with file
  93                        reservations - users should rarely need to change this
  94                        value. If allocation reservations are turned off, this
  95                        option will have no effect.
  96coherency=full  (*)     Disallow concurrent O_DIRECT writes, cluster inode
  97                        lock will be taken to force other nodes drop cache,
  98                        therefore full cluster coherency is guaranteed even
  99                        for O_DIRECT writes.
 100coherency=buffered      Allow concurrent O_DIRECT writes without EX lock among
 101                        nodes, which gains high performance at risk of getting
 102                        stale data on other nodes.