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   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.
  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         the default allocation option. Applications which do not handle
  76         inode numbers bigger than 32 bits, should use inode32 option.
  77
  78   inode32
  79         Indicates that XFS is limited to create inodes at locations which
  80         will not result in inode numbers with more than 32 bits of
  81         significance. This is provided for backwards compatibility, since
  82         64 bits inode numbers might cause problems for some applications
  83         that cannot handle large inode numbers.
  84
  85   largeio/nolargeio
  86         If "nolargeio" is specified, the optimal I/O reported in
  87         st_blksize by stat(2) will be as small as possible to allow user
  88         applications to avoid inefficient read/modify/write I/O.
  89         If "largeio" specified, a filesystem that has a "swidth" specified
  90         will return the "swidth" value (in bytes) in st_blksize. If the
  91         filesystem does not have a "swidth" specified but does specify
  92         an "allocsize" then "allocsize" (in bytes) will be returned
  93         instead.
  94         If neither of these two options are specified, then filesystem
  95         will behave as if "nolargeio" was specified.
  96
  97   logbufs=value
  98         Set the number of in-memory log buffers.  Valid numbers range
  99         from 2-8 inclusive.
 100         The default value is 8 buffers for filesystems with a
 101         blocksize of 64KiB, 4 buffers for filesystems with a blocksize
 102         of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB
 103         and 2 buffers for all other configurations.  Increasing the
 104         number of buffers may increase performance on some workloads
 105         at the cost of the memory used for the additional log buffers
 106         and their associated control structures.
 107
 108   logbsize=value
 109         Set the size of each in-memory log buffer.
 110         Size may be specified in bytes, or in kilobytes with a "k" suffix.
 111         Valid sizes for version 1 and version 2 logs are 16384 (16k) and
 112         32768 (32k).  Valid sizes for version 2 logs also include
 113         65536 (64k), 131072 (128k) and 262144 (256k).
 114         The default value for machines with more than 32MiB of memory
 115         is 32768, machines with less memory use 16384 by default.
 116
 117   logdev=device and rtdev=device
 118         Use an external log (metadata journal) and/or real-time device.
 119         An XFS filesystem has up to three parts: a data section, a log
 120         section, and a real-time section.  The real-time section is
 121         optional, and the log section can be separate from the data
 122         section or contained within it.
 123
 124   mtpt=mountpoint
 125         Use with the "dmapi" option.  The value specified here will be
 126         included in the DMAPI mount event, and should be the path of
 127         the actual mountpoint that is used.
 128
 129   noalign
 130         Data allocations will not be aligned at stripe unit boundaries.
 131
 132   noatime
 133         Access timestamps are not updated when a file is read.
 134
 135   norecovery
 136         The filesystem will be mounted without running log recovery.
 137         If the filesystem was not cleanly unmounted, it is likely to
 138         be inconsistent when mounted in "norecovery" mode.
 139         Some files or directories may not be accessible because of this.
 140         Filesystems mounted "norecovery" must be mounted read-only or
 141         the mount will fail.
 142
 143   nouuid
 144         Don't check for double mounted file systems using the file system uuid.
 145         This is useful to mount LVM snapshot volumes.
 146
 147   uquota/usrquota/uqnoenforce/quota
 148         User disk quota accounting enabled, and limits (optionally)
 149         enforced.  Refer to xfs_quota(8) for further details.
 150
 151   gquota/grpquota/gqnoenforce
 152         Group disk quota accounting enabled and limits (optionally)
 153         enforced.  Refer to xfs_quota(8) for further details.
 154
 155   pquota/prjquota/pqnoenforce
 156         Project disk quota accounting enabled and limits (optionally)
 157         enforced.  Refer to xfs_quota(8) for further details.
 158
 159   sunit=value and swidth=value
 160         Used to specify the stripe unit and width for a RAID device or
 161         a stripe volume.  "value" must be specified in 512-byte block
 162         units.
 163         If this option is not specified and the filesystem was made on
 164         a stripe volume or the stripe width or unit were specified for
 165         the RAID device at mkfs time, then the mount system call will
 166         restore the value from the superblock.  For filesystems that
 167         are made directly on RAID devices, these options can be used
 168         to override the information in the superblock if the underlying
 169         disk layout changes after the filesystem has been created.
 170         The "swidth" option is required if the "sunit" option has been
 171         specified, and must be a multiple of the "sunit" value.
 172
 173   swalloc
 174         Data allocations will be rounded up to stripe width boundaries
 175         when the current end of file is being extended and the file
 176         size is larger than the stripe width size.
 177
 178
 179 sysctls
 180 =======
 181
 182 The following sysctls are available for the XFS filesystem:
 183
 184   fs.xfs.stats_clear            (Min: 0  Default: 0  Max: 1)
 185         Setting this to "1" clears accumulated XFS statistics
 186         in /proc/fs/xfs/stat.  It then immediately resets to "0".
 187
 188   fs.xfs.xfssyncd_centisecs     (Min: 100  Default: 3000  Max: 720000)
 189         The interval at which the xfssyncd thread flushes metadata
 190         out to disk.  This thread will flush log activity out, and
 191         do some processing on unlinked inodes.
 192
 193   fs.xfs.xfsbufd_centisecs      (Min: 50  Default: 100  Max: 3000)
 194         The interval at which xfsbufd scans the dirty metadata buffers list.
 195
 196   fs.xfs.age_buffer_centisecs   (Min: 100  Default: 1500  Max: 720000)
 197         The age at which xfsbufd flushes dirty metadata buffers to disk.
 198
 199   fs.xfs.error_level            (Min: 0  Default: 3  Max: 11)
 200         A volume knob for error reporting when internal errors occur.
 201         This will generate detailed messages & backtraces for filesystem
 202         shutdowns, for example.  Current threshold values are:
 203
 204                 XFS_ERRLEVEL_OFF:       0
 205                 XFS_ERRLEVEL_LOW:       1
 206                 XFS_ERRLEVEL_HIGH:      5
 207
 208   fs.xfs.panic_mask             (Min: 0  Default: 0  Max: 127)
 209         Causes certain error conditions to call BUG(). Value is a bitmask;
 210         AND together the tags which represent errors which should cause panics:
 211
 212                 XFS_NO_PTAG                     0
 213                 XFS_PTAG_IFLUSH                 0x00000001
 214                 XFS_PTAG_LOGRES                 0x00000002
 215                 XFS_PTAG_AILDELETE              0x00000004
 216                 XFS_PTAG_ERROR_REPORT           0x00000008
 217                 XFS_PTAG_SHUTDOWN_CORRUPT       0x00000010
 218                 XFS_PTAG_SHUTDOWN_IOERROR       0x00000020
 219                 XFS_PTAG_SHUTDOWN_LOGERROR      0x00000040
 220
 221         This option is intended for debugging only.
 222
 223   fs.xfs.irix_symlink_mode      (Min: 0  Default: 0  Max: 1)
 224         Controls whether symlinks are created with mode 0777 (default)
 225         or whether their mode is affected by the umask (irix mode).
 226
 227   fs.xfs.irix_sgid_inherit      (Min: 0  Default: 0  Max: 1)
 228         Controls files created in SGID directories.
 229         If the group ID of the new file does not match the effective group
 230         ID or one of the supplementary group IDs of the parent dir, the
 231         ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
 232         is set.
 233
 234   fs.xfs.inherit_sync           (Min: 0  Default: 1  Max: 1)
 235         Setting this to "1" will cause the "sync" flag set
 236         by the xfs_io(8) chattr command on a directory to be
 237         inherited by files in that directory.
 238
 239   fs.xfs.inherit_nodump         (Min: 0  Default: 1  Max: 1)
 240         Setting this to "1" will cause the "nodump" flag set
 241         by the xfs_io(8) chattr command on a directory to be
 242         inherited by files in that directory.
 243
 244   fs.xfs.inherit_noatime        (Min: 0  Default: 1  Max: 1)
 245         Setting this to "1" will cause the "noatime" flag set
 246         by the xfs_io(8) chattr command on a directory to be
 247         inherited by files in that directory.
 248
 249   fs.xfs.inherit_nosymlinks     (Min: 0  Default: 1  Max: 1)
 250         Setting this to "1" will cause the "nosymlinks" flag set
 251         by the xfs_io(8) chattr command on a directory to be
 252         inherited by files in that directory.
 253
 254   fs.xfs.rotorstep              (Min: 1  Default: 1  Max: 256)
 255         In "inode32" allocation mode, this option determines how many
 256         files the allocator attempts to allocate in the same allocation
 257         group before moving to the next allocation group.  The intent
 258         is to control the rate at which the allocator moves between
 259         allocation groups when allocating extents for new files.