Documentation/filesystems/xfs.txt

   1
   2 The SGI XFS Filesystem
   3 ======================
   4
   5 XFS is a high performance journaling filesystem which originated
   6 on the SGI IRIX platform.  It is completely multi-threaded, can
   7 support large files and large filesystems, extended attributes,
   8 variable block sizes, is extent based, and makes extensive use of
   9 Btrees (directories, extents, free space) to aid both performance
  10 and scalability.
  11
  12 Refer to the documentation at http://oss.sgi.com/projects/xfs/
  13 for further details.  This implementation is on-disk compatible
  14 with the IRIX version of XFS.
  15
  16
  17 Mount Options
  18 =============
  19
  20 When mounting an XFS filesystem, the following options are accepted.
  21
  22   biosize=size
  23         Sets the preferred buffered I/O size (default size is 64K).
  24         "size" must be expressed as the logarithm (base2) of the
  25         desired I/O size.
  26         Valid values for this option are 14 through 16, inclusive
  27         (i.e. 16K, 32K, and 64K bytes).  On machines with a 4K
  28         pagesize, 13 (8K bytes) is also a valid size.
  29         The preferred buffered I/O size can also be altered on an
  30         individual file basis using the ioctl(2) system call.
  31
  32   ikeep/noikeep
  33         When inode clusters are emptied of inodes, keep them around
  34         on the disk (ikeep) - this is the traditional XFS behaviour
  35         and is still the default for now.  Using the noikeep option,
  36         inode clusters are returned to the free space pool.
  37
  38   logbufs=value
  39         Set the number of in-memory log buffers.  Valid numbers range
  40         from 2-8 inclusive.
  41         The default value is 8 buffers for filesystems with a
  42         blocksize of 64K, 4 buffers for filesystems with a blocksize
  43         of 32K, 3 buffers for filesystems with a blocksize of 16K
  44         and 2 buffers for all other configurations.  Increasing the
  45         number of buffers may increase performance on some workloads
  46         at the cost of the memory used for the additional log buffers
  47         and their associated control structures.
  48
  49   logbsize=value
  50         Set the size of each in-memory log buffer.
  51         Size may be specified in bytes, or in kilobytes with a "k" suffix.
  52         Valid sizes for version 1 and version 2 logs are 16384 (16k) and
  53         32768 (32k).  Valid sizes for version 2 logs also include
  54         65536 (64k), 131072 (128k) and 262144 (256k).
  55         The default value for machines with more than 32MB of memory
  56         is 32768, machines with less memory use 16384 by default.
  57
  58   logdev=device and rtdev=device
  59         Use an external log (metadata journal) and/or real-time device.
  60         An XFS filesystem has up to three parts: a data section, a log
  61         section, and a real-time section.  The real-time section is
  62         optional, and the log section can be separate from the data
  63         section or contained within it.
  64
  65   noalign
  66         Data allocations will not be aligned at stripe unit boundaries.
  67
  68   noatime
  69         Access timestamps are not updated when a file is read.
  70
  71   norecovery
  72         The filesystem will be mounted without running log recovery.
  73         If the filesystem was not cleanly unmounted, it is likely to
  74         be inconsistent when mounted in "norecovery" mode.
  75         Some files or directories may not be accessible because of this.
  76         Filesystems mounted "norecovery" must be mounted read-only or
  77         the mount will fail.
  78
  79   nouuid
  80         Don't check for double mounted file systems using the file system uuid.
  81         This is useful to mount LVM snapshot volumes.
  82
  83   osyncisosync
  84         Make O_SYNC writes implement true O_SYNC.  WITHOUT this option,
  85         Linux XFS behaves as if an "osyncisdsync" option is used,
  86         which will make writes to files opened with the O_SYNC flag set
  87         behave as if the O_DSYNC flag had been used instead.
  88         This can result in better performance without compromising
  89         data safety.
  90         However if this option is not in effect, timestamp updates from
  91         O_SYNC writes can be lost if the system crashes.
  92         If timestamp updates are critical, use the osyncisosync option.
  93
  94   quota/usrquota/uqnoenforce
  95         User disk quota accounting enabled, and limits (optionally)
  96         enforced.
  97
  98   grpquota/gqnoenforce
  99         Group disk quota accounting enabled and limits (optionally)
 100         enforced.
 101
 102   sunit=value and swidth=value
 103         Used to specify the stripe unit and width for a RAID device or
 104         a stripe volume.  "value" must be specified in 512-byte block
 105         units.
 106         If this option is not specified and the filesystem was made on
 107         a stripe volume or the stripe width or unit were specified for
 108         the RAID device at mkfs time, then the mount system call will
 109         restore the value from the superblock.  For filesystems that
 110         are made directly on RAID devices, these options can be used
 111         to override the information in the superblock if the underlying
 112         disk layout changes after the filesystem has been created.
 113         The "swidth" option is required if the "sunit" option has been
 114         specified, and must be a multiple of the "sunit" value.
 115
 116 sysctls
 117 =======
 118
 119 The following sysctls are available for the XFS filesystem:
 120
 121   fs.xfs.stats_clear            (Min: 0  Default: 0  Max: 1)
 122         Setting this to "1" clears accumulated XFS statistics
 123         in /proc/fs/xfs/stat.  It then immediately resets to "0".
 124
 125   fs.xfs.xfssyncd_centisecs     (Min: 100  Default: 3000  Max: 720000)
 126         The interval at which the xfssyncd thread flushes metadata
 127         out to disk.  This thread will flush log activity out, and
 128         do some processing on unlinked inodes.
 129
 130   fs.xfs.xfsbufd_centisecs      (Min: 50  Default: 100  Max: 3000)
 131         The interval at which xfsbufd scans the dirty metadata buffers list.
 132
 133   fs.xfs.age_buffer_centisecs   (Min: 100  Default: 1500  Max: 720000)
 134         The age at which xfsbufd flushes dirty metadata buffers to disk.
 135
 136   fs.xfs.error_level            (Min: 0  Default: 3  Max: 11)
 137         A volume knob for error reporting when internal errors occur.
 138         This will generate detailed messages & backtraces for filesystem
 139         shutdowns, for example.  Current threshold values are:
 140
 141                 XFS_ERRLEVEL_OFF:       0
 142                 XFS_ERRLEVEL_LOW:       1
 143                 XFS_ERRLEVEL_HIGH:      5
 144
 145   fs.xfs.panic_mask             (Min: 0  Default: 0  Max: 127)
 146         Causes certain error conditions to call BUG(). Value is a bitmask;
 147         AND together the tags which represent errors which should cause panics:
 148
 149                 XFS_NO_PTAG                     0
 150                 XFS_PTAG_IFLUSH                 0x00000001
 151                 XFS_PTAG_LOGRES                 0x00000002
 152                 XFS_PTAG_AILDELETE              0x00000004
 153                 XFS_PTAG_ERROR_REPORT           0x00000008
 154                 XFS_PTAG_SHUTDOWN_CORRUPT       0x00000010
 155                 XFS_PTAG_SHUTDOWN_IOERROR       0x00000020
 156                 XFS_PTAG_SHUTDOWN_LOGERROR      0x00000040
 157
 158         This option is intended for debugging only.
 159
 160   fs.xfs.irix_symlink_mode      (Min: 0  Default: 0  Max: 1)
 161         Controls whether symlinks are created with mode 0777 (default)
 162         or whether their mode is affected by the umask (irix mode).
 163
 164   fs.xfs.irix_sgid_inherit      (Min: 0  Default: 0  Max: 1)
 165         Controls files created in SGID directories.
 166         If the group ID of the new file does not match the effective group
 167         ID or one of the supplementary group IDs of the parent dir, the
 168         ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
 169         is set.
 170
 171   fs.xfs.restrict_chown         (Min: 0  Default: 1  Max: 1)
 172         Controls whether unprivileged users can use chown to "give away"
 173         a file to another user.
 174
 175   fs.xfs.inherit_sync           (Min: 0  Default: 1  Max 1)
 176         Setting this to "1" will cause the "sync" flag set
 177         by the chattr(1) command on a directory to be
 178         inherited by files in that directory.
 179
 180   fs.xfs.inherit_nodump         (Min: 0  Default: 1  Max 1)
 181         Setting this to "1" will cause the "nodump" flag set
 182         by the chattr(1) command on a directory to be
 183         inherited by files in that directory.
 184
 185   fs.xfs.inherit_noatime        (Min: 0  Default: 1  Max 1)
 186         Setting this to "1" will cause the "noatime" flag set
 187         by the chattr(1) command on a directory to be
 188         inherited by files in that directory.