Documentation/filesystems/ocfs2.txt

   1 OCFS2 filesystem
   2 ==================
   3 OCFS2 is a general purpose extent based shared disk cluster file
   4 system with many similarities to ext3. It supports 64 bit inode
   5 numbers, and has automatically extending metadata groups which may
   6 also make it attractive for non-clustered use.
   7
   8 You'll want to install the ocfs2-tools package in order to at least
   9 get "mount.ocfs2" and "ocfs2_hb_ctl".
  10
  11 Project web page:    http://ocfs2.wiki.kernel.org
  12 Tools git tree:      https://github.com/markfasheh/ocfs2-tools
  13 OCFS2 mailing lists: http://oss.oracle.com/projects/ocfs2/mailman/
  14
  15 All code copyright 2005 Oracle except when otherwise noted.
  16
  17 CREDITS:
  18 Lots of code taken from ext3 and other projects.
  19
  20 Authors in alphabetical order:
  21 Joel Becker   <joel.becker@oracle.com>
  22 Zach Brown    <zach.brown@oracle.com>
  23 Mark Fasheh   <mfasheh@suse.com>
  24 Kurt Hackel   <kurt.hackel@oracle.com>
  25 Tao Ma        <tao.ma@oracle.com>
  26 Sunil Mushran <sunil.mushran@oracle.com>
  27 Manish Singh  <manish.singh@oracle.com>
  28 Tiger Yang    <tiger.yang@oracle.com>
  29
  30 Caveats
  31 =======
  32 Features which OCFS2 does not support yet:
  33         - Directory change notification (F_NOTIFY)
  34         - Distributed Caching (F_SETLEASE/F_GETLEASE/break_lease)
  35
  36 Mount options
  37 =============
  38
  39 OCFS2 supports the following mount options:
  40 (*) == default
  41
  42 barrier=1               This enables/disables barriers. barrier=0 disables it,
  43                         barrier=1 enables it.
  44 errors=remount-ro(*)    Remount the filesystem read-only on an error.
  45 errors=panic            Panic and halt the machine if an error occurs.
  46 intr            (*)     Allow signals to interrupt cluster operations.
  47 nointr                  Do not allow signals to interrupt cluster
  48                         operations.
  49 noatime                 Do not update access time.
  50 relatime(*)             Update atime if the previous atime is older than
  51                         mtime or ctime
  52 strictatime             Always update atime, but the minimum update interval
  53                         is specified by atime_quantum.
  54 atime_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.
  58 data=ordered    (*)     All data are forced directly out to the main file
  59                         system prior to its metadata being committed to the
  60                         journal.
  61 data=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.
  64 preferred_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.
  67 commit=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.
  78 localalloc=8(*)         Allows custom localalloc size in MB. If the value is too
  79                         large, the fs will silently revert it to the default.
  80 localflocks             This disables cluster aware flock.
  81 inode64                 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.
  85 user_xattr      (*)     Enables Extended User Attributes.
  86 nouser_xattr            Disables Extended User Attributes.
  87 acl                     Enables POSIX Access Control Lists support.
  88 noacl           (*)     Disables POSIX Access Control Lists support.
  89 resv_level=2    (*)     Set how aggressive allocation reservations will be.
  90                         Valid values are between 0 (reservations off) to 8
  91                         (maximum space for reservations).
  92 dir_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.
  96 coherency=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.
 100 coherency=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.
 103 journal_async_commit    Commit block can be written to disk without waiting
 104                         for descriptor blocks. If enabled older kernels cannot
 105                         mount the device. This will enable 'journal_checksum'
 106                         internally.