linux/Documentation/filesystems/xfs.txt
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   1
   2The SGI XFS Filesystem
   3======================
   4
   5XFS is a high performance journaling filesystem which originated
   6on the SGI IRIX platform.  It is completely multi-threaded, can
   7support large files and large filesystems, extended attributes,
   8variable block sizes, is extent based, and makes extensive use of
   9Btrees (directories, extents, free space) to aid both performance
  10and scalability.
  11
  12Refer to the documentation at http://oss.sgi.com/projects/xfs/
  13for further details.  This implementation is on-disk compatible
  14with the IRIX version of XFS.
  15
  16
  17Mount Options
  18=============
  19
  20When mounting an XFS filesystem, the following options are accepted.
  21
  22  allocsize=size
  23        Sets the buffered I/O end-of-file preallocation size when
  24        doing delayed allocation writeout (default size is 64KiB).
  25        Valid values for this option are page size (typically 4KiB)
  26        through to 1GiB, inclusive, in power-of-2 increments.
  27
  28  attr2/noattr2
  29        The options enable/disable (default is disabled for backward
  30        compatibility on-disk) an "opportunistic" improvement to be
  31        made in the way inline extended attributes are stored on-disk.
  32        When the new form is used for the first time (by setting or
  33        removing extended attributes) the on-disk superblock feature
  34        bit field will be updated to reflect this format being in use.
  35
  36  barrier
  37        Enables the use of block layer write barriers for writes into
  38        the journal and unwritten extent conversion.  This allows for
  39        drive level write caching to be enabled, for devices that
  40        support write barriers.
  41
  42  discard
  43        Issue command to let the block device reclaim space freed by the
  44        filesystem.  This is useful for SSD devices, thinly provisioned
  45        LUNs and virtual machine images, but may have a performance
  46        impact.  This option is incompatible with the nodelaylog option.
  47
  48  dmapi
  49        Enable the DMAPI (Data Management API) event callouts.
  50        Use with the "mtpt" option.
  51
  52  grpid/bsdgroups and nogrpid/sysvgroups
  53        These options define what group ID a newly created file gets.
  54        When grpid is set, it takes the group ID of the directory in
  55        which it is created; otherwise (the default) it takes the fsgid
  56        of the current process, unless the directory has the setgid bit
  57        set, in which case it takes the gid from the parent directory,
  58        and also gets the setgid bit set if it is a directory itself.
  59
  60  ihashsize=value
  61        In memory inode hashes have been removed, so this option has
  62        no function as of August 2007. Option is deprecated.
  63
  64  ikeep/noikeep
  65        When ikeep is specified, XFS does not delete empty inode clusters
  66        and keeps them around on disk. ikeep is the traditional XFS
  67        behaviour. When noikeep is specified, empty inode clusters
  68        are returned to the free space pool. The default is noikeep for
  69        non-DMAPI mounts, while ikeep is the default when DMAPI is in use.
  70
  71  inode64
  72        Indicates that XFS is allowed to create inodes at any location
  73        in the filesystem, including those which will result in inode
  74        numbers occupying more than 32 bits of significance.  This is
  75        provided for backwards compatibility, but causes problems for
  76        backup applications that cannot handle large inode numbers.
  77
  78  largeio/nolargeio
  79        If "nolargeio" is specified, the optimal I/O reported in
  80        st_blksize by stat(2) will be as small as possible to allow user
  81        applications to avoid inefficient read/modify/write I/O.
  82        If "largeio" specified, a filesystem that has a "swidth" specified
  83        will return the "swidth" value (in bytes) in st_blksize. If the
  84        filesystem does not have a "swidth" specified but does specify
  85        an "allocsize" then "allocsize" (in bytes) will be returned
  86        instead.
  87        If neither of these two options are specified, then filesystem
  88        will behave as if "nolargeio" was specified.
  89
  90  logbufs=value
  91        Set the number of in-memory log buffers.  Valid numbers range
  92        from 2-8 inclusive.
  93        The default value is 8 buffers for filesystems with a
  94        blocksize of 64KiB, 4 buffers for filesystems with a blocksize
  95        of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB
  96        and 2 buffers for all other configurations.  Increasing the
  97        number of buffers may increase performance on some workloads
  98        at the cost of the memory used for the additional log buffers
  99        and their associated control structures.
 100
 101  logbsize=value
 102        Set the size of each in-memory log buffer.
 103        Size may be specified in bytes, or in kilobytes with a "k" suffix.
 104        Valid sizes for version 1 and version 2 logs are 16384 (16k) and
 105        32768 (32k).  Valid sizes for version 2 logs also include
 106        65536 (64k), 131072 (128k) and 262144 (256k).
 107        The default value for machines with more than 32MiB of memory
 108        is 32768, machines with less memory use 16384 by default.
 109
 110  logdev=device and rtdev=device
 111        Use an external log (metadata journal) and/or real-time device.
 112        An XFS filesystem has up to three parts: a data section, a log
 113        section, and a real-time section.  The real-time section is
 114        optional, and the log section can be separate from the data
 115        section or contained within it.
 116
 117  mtpt=mountpoint
 118        Use with the "dmapi" option.  The value specified here will be
 119        included in the DMAPI mount event, and should be the path of
 120        the actual mountpoint that is used.
 121
 122  noalign
 123        Data allocations will not be aligned at stripe unit boundaries.
 124
 125  noatime
 126        Access timestamps are not updated when a file is read.
 127
 128  norecovery
 129        The filesystem will be mounted without running log recovery.
 130        If the filesystem was not cleanly unmounted, it is likely to
 131        be inconsistent when mounted in "norecovery" mode.
 132        Some files or directories may not be accessible because of this.
 133        Filesystems mounted "norecovery" must be mounted read-only or
 134        the mount will fail.
 135
 136  nouuid
 137        Don't check for double mounted file systems using the file system uuid.
 138        This is useful to mount LVM snapshot volumes.
 139
 140  uquota/usrquota/uqnoenforce/quota
 141        User disk quota accounting enabled, and limits (optionally)
 142        enforced.  Refer to xfs_quota(8) for further details.
 143
 144  gquota/grpquota/gqnoenforce
 145        Group disk quota accounting enabled and limits (optionally)
 146        enforced.  Refer to xfs_quota(8) for further details.
 147
 148  pquota/prjquota/pqnoenforce
 149        Project disk quota accounting enabled and limits (optionally)
 150        enforced.  Refer to xfs_quota(8) for further details.
 151
 152  sunit=value and swidth=value
 153        Used to specify the stripe unit and width for a RAID device or
 154        a stripe volume.  "value" must be specified in 512-byte block
 155        units.
 156        If this option is not specified and the filesystem was made on
 157        a stripe volume or the stripe width or unit were specified for
 158        the RAID device at mkfs time, then the mount system call will
 159        restore the value from the superblock.  For filesystems that
 160        are made directly on RAID devices, these options can be used
 161        to override the information in the superblock if the underlying
 162        disk layout changes after the filesystem has been created.
 163        The "swidth" option is required if the "sunit" option has been
 164        specified, and must be a multiple of the "sunit" value.
 165
 166  swalloc
 167        Data allocations will be rounded up to stripe width boundaries
 168        when the current end of file is being extended and the file
 169        size is larger than the stripe width size.
 170
 171
 172sysctls
 173=======
 174
 175The following sysctls are available for the XFS filesystem:
 176
 177  fs.xfs.stats_clear            (Min: 0  Default: 0  Max: 1)
 178        Setting this to "1" clears accumulated XFS statistics
 179        in /proc/fs/xfs/stat.  It then immediately resets to "0".
 180
 181  fs.xfs.xfssyncd_centisecs     (Min: 100  Default: 3000  Max: 720000)
 182        The interval at which the xfssyncd thread flushes metadata
 183        out to disk.  This thread will flush log activity out, and
 184        do some processing on unlinked inodes.
 185
 186  fs.xfs.xfsbufd_centisecs      (Min: 50  Default: 100  Max: 3000)
 187        The interval at which xfsbufd scans the dirty metadata buffers list.
 188
 189  fs.xfs.age_buffer_centisecs   (Min: 100  Default: 1500  Max: 720000)
 190        The age at which xfsbufd flushes dirty metadata buffers to disk.
 191
 192  fs.xfs.error_level            (Min: 0  Default: 3  Max: 11)
 193        A volume knob for error reporting when internal errors occur.
 194        This will generate detailed messages & backtraces for filesystem
 195        shutdowns, for example.  Current threshold values are:
 196
 197                XFS_ERRLEVEL_OFF:       0
 198                XFS_ERRLEVEL_LOW:       1
 199                XFS_ERRLEVEL_HIGH:      5
 200
 201  fs.xfs.panic_mask             (Min: 0  Default: 0  Max: 127)
 202        Causes certain error conditions to call BUG(). Value is a bitmask;
 203        AND together the tags which represent errors which should cause panics:
 204
 205                XFS_NO_PTAG                     0
 206                XFS_PTAG_IFLUSH                 0x00000001
 207                XFS_PTAG_LOGRES                 0x00000002
 208                XFS_PTAG_AILDELETE              0x00000004
 209                XFS_PTAG_ERROR_REPORT           0x00000008
 210                XFS_PTAG_SHUTDOWN_CORRUPT       0x00000010
 211                XFS_PTAG_SHUTDOWN_IOERROR       0x00000020
 212                XFS_PTAG_SHUTDOWN_LOGERROR      0x00000040
 213
 214        This option is intended for debugging only.
 215
 216  fs.xfs.irix_symlink_mode      (Min: 0  Default: 0  Max: 1)
 217        Controls whether symlinks are created with mode 0777 (default)
 218        or whether their mode is affected by the umask (irix mode).
 219
 220  fs.xfs.irix_sgid_inherit      (Min: 0  Default: 0  Max: 1)
 221        Controls files created in SGID directories.
 222        If the group ID of the new file does not match the effective group
 223        ID or one of the supplementary group IDs of the parent dir, the
 224        ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
 225        is set.
 226
 227  fs.xfs.inherit_sync           (Min: 0  Default: 1  Max: 1)
 228        Setting this to "1" will cause the "sync" flag set
 229        by the xfs_io(8) chattr command on a directory to be
 230        inherited by files in that directory.
 231
 232  fs.xfs.inherit_nodump         (Min: 0  Default: 1  Max: 1)
 233        Setting this to "1" will cause the "nodump" flag set
 234        by the xfs_io(8) chattr command on a directory to be
 235        inherited by files in that directory.
 236
 237  fs.xfs.inherit_noatime        (Min: 0  Default: 1  Max: 1)
 238        Setting this to "1" will cause the "noatime" flag set
 239        by the xfs_io(8) chattr command on a directory to be
 240        inherited by files in that directory.
 241
 242  fs.xfs.inherit_nosymlinks     (Min: 0  Default: 1  Max: 1)
 243        Setting this to "1" will cause the "nosymlinks" flag set
 244        by the xfs_io(8) chattr command on a directory to be
 245        inherited by files in that directory.
 246
 247  fs.xfs.rotorstep              (Min: 1  Default: 1  Max: 256)
 248        In "inode32" allocation mode, this option determines how many
 249        files the allocator attempts to allocate in the same allocation
 250        group before moving to the next allocation group.  The intent
 251        is to control the rate at which the allocator moves between
 252        allocation groups when allocating extents for new files.
 253
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