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-
-The SGI XFS Filesystem
-======================
-
-XFS is a high performance journaling filesystem which originated
-on the SGI IRIX platform. It is completely multi-threaded, can
-support large files and large filesystems, extended attributes,
-variable block sizes, is extent based, and makes extensive use of
-Btrees (directories, extents, free space) to aid both performance
-and scalability.
-
-Refer to the documentation at http://oss.sgi.com/projects/xfs/
-for further details. This implementation is on-disk compatible
-with the IRIX version of XFS.
-
-
-Mount Options
-=============
-
-When mounting an XFS filesystem, the following options are accepted.
-
- allocsize=size
- Sets the buffered I/O end-of-file preallocation size when
- doing delayed allocation writeout (default size is 64KiB).
- Valid values for this option are page size (typically 4KiB)
- through to 1GiB, inclusive, in power-of-2 increments.
-
- attr2/noattr2
- The options enable/disable (default is disabled for backward
- compatibility on-disk) an "opportunistic" improvement to be
- made in the way inline extended attributes are stored on-disk.
- When the new form is used for the first time (by setting or
- removing extended attributes) the on-disk superblock feature
- bit field will be updated to reflect this format being in use.
-
- barrier
- Enables the use of block layer write barriers for writes into
- the journal and unwritten extent conversion. This allows for
- drive level write caching to be enabled, for devices that
- support write barriers.
-
- discard
- Issue command to let the block device reclaim space freed by the
- filesystem. This is useful for SSD devices, thinly provisioned
- LUNs and virtual machine images, but may have a performance
- impact. This option is incompatible with the nodelaylog option.
-
- dmapi
- Enable the DMAPI (Data Management API) event callouts.
- Use with the "mtpt" option.
-
- grpid/bsdgroups and nogrpid/sysvgroups
- These options define what group ID a newly created file gets.
- When grpid is set, it takes the group ID of the directory in
- which it is created; otherwise (the default) it takes the fsgid
- of the current process, unless the directory has the setgid bit
- set, in which case it takes the gid from the parent directory,
- and also gets the setgid bit set if it is a directory itself.
-
- ihashsize=value
- In memory inode hashes have been removed, so this option has
- no function as of August 2007. Option is deprecated.
-
- ikeep/noikeep
- When ikeep is specified, XFS does not delete empty inode clusters
- and keeps them around on disk. ikeep is the traditional XFS
- behaviour. When noikeep is specified, empty inode clusters
- are returned to the free space pool. The default is noikeep for
- non-DMAPI mounts, while ikeep is the default when DMAPI is in use.
-
- inode64
- Indicates that XFS is allowed to create inodes at any location
- in the filesystem, including those which will result in inode
- numbers occupying more than 32 bits of significance. This is
- provided for backwards compatibility, but causes problems for
- backup applications that cannot handle large inode numbers.
-
- largeio/nolargeio
- If "nolargeio" is specified, the optimal I/O reported in
- st_blksize by stat(2) will be as small as possible to allow user
- applications to avoid inefficient read/modify/write I/O.
- If "largeio" specified, a filesystem that has a "swidth" specified
- will return the "swidth" value (in bytes) in st_blksize. If the
- filesystem does not have a "swidth" specified but does specify
- an "allocsize" then "allocsize" (in bytes) will be returned
- instead.
- If neither of these two options are specified, then filesystem
- will behave as if "nolargeio" was specified.
-
- logbufs=value
- Set the number of in-memory log buffers. Valid numbers range
- from 2-8 inclusive.
- The default value is 8 buffers for filesystems with a
- blocksize of 64KiB, 4 buffers for filesystems with a blocksize
- of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB
- and 2 buffers for all other configurations. Increasing the
- number of buffers may increase performance on some workloads
- at the cost of the memory used for the additional log buffers
- and their associated control structures.
-
- logbsize=value
- Set the size of each in-memory log buffer.
- Size may be specified in bytes, or in kilobytes with a "k" suffix.
- Valid sizes for version 1 and version 2 logs are 16384 (16k) and
- 32768 (32k). Valid sizes for version 2 logs also include
- 65536 (64k), 131072 (128k) and 262144 (256k).
- The default value for machines with more than 32MiB of memory
- is 32768, machines with less memory use 16384 by default.
-
- logdev=device and rtdev=device
- Use an external log (metadata journal) and/or real-time device.
- An XFS filesystem has up to three parts: a data section, a log
- section, and a real-time section. The real-time section is
- optional, and the log section can be separate from the data
- section or contained within it.
-
- mtpt=mountpoint
- Use with the "dmapi" option. The value specified here will be
- included in the DMAPI mount event, and should be the path of
- the actual mountpoint that is used.
-
- noalign
- Data allocations will not be aligned at stripe unit boundaries.
-
- noatime
- Access timestamps are not updated when a file is read.
-
- norecovery
- The filesystem will be mounted without running log recovery.
- If the filesystem was not cleanly unmounted, it is likely to
- be inconsistent when mounted in "norecovery" mode.
- Some files or directories may not be accessible because of this.
- Filesystems mounted "norecovery" must be mounted read-only or
- the mount will fail.
-
- nouuid
- Don't check for double mounted file systems using the file system uuid.
- This is useful to mount LVM snapshot volumes.
-
- uquota/usrquota/uqnoenforce/quota
- User disk quota accounting enabled, and limits (optionally)
- enforced. Refer to xfs_quota(8) for further details.
-
- gquota/grpquota/gqnoenforce
- Group disk quota accounting enabled and limits (optionally)
- enforced. Refer to xfs_quota(8) for further details.
-
- pquota/prjquota/pqnoenforce
- Project disk quota accounting enabled and limits (optionally)
- enforced. Refer to xfs_quota(8) for further details.
-
- sunit=value and swidth=value
- Used to specify the stripe unit and width for a RAID device or
- a stripe volume. "value" must be specified in 512-byte block
- units.
- If this option is not specified and the filesystem was made on
- a stripe volume or the stripe width or unit were specified for
- the RAID device at mkfs time, then the mount system call will
- restore the value from the superblock. For filesystems that
- are made directly on RAID devices, these options can be used
- to override the information in the superblock if the underlying
- disk layout changes after the filesystem has been created.
- The "swidth" option is required if the "sunit" option has been
- specified, and must be a multiple of the "sunit" value.
-
- swalloc
- Data allocations will be rounded up to stripe width boundaries
- when the current end of file is being extended and the file
- size is larger than the stripe width size.
-
-
-sysctls
-=======
-
-The following sysctls are available for the XFS filesystem:
-
- fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1)
- Setting this to "1" clears accumulated XFS statistics
- in /proc/fs/xfs/stat. It then immediately resets to "0".
-
- fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000)
- The interval at which the xfssyncd thread flushes metadata
- out to disk. This thread will flush log activity out, and
- do some processing on unlinked inodes.
-
- fs.xfs.xfsbufd_centisecs (Min: 50 Default: 100 Max: 3000)
- The interval at which xfsbufd scans the dirty metadata buffers list.
-
- fs.xfs.age_buffer_centisecs (Min: 100 Default: 1500 Max: 720000)
- The age at which xfsbufd flushes dirty metadata buffers to disk.
-
- fs.xfs.error_level (Min: 0 Default: 3 Max: 11)
- A volume knob for error reporting when internal errors occur.
- This will generate detailed messages & backtraces for filesystem
- shutdowns, for example. Current threshold values are:
-
- XFS_ERRLEVEL_OFF: 0
- XFS_ERRLEVEL_LOW: 1
- XFS_ERRLEVEL_HIGH: 5
-
- fs.xfs.panic_mask (Min: 0 Default: 0 Max: 127)
- Causes certain error conditions to call BUG(). Value is a bitmask;
- AND together the tags which represent errors which should cause panics:
-
- XFS_NO_PTAG 0
- XFS_PTAG_IFLUSH 0x00000001
- XFS_PTAG_LOGRES 0x00000002
- XFS_PTAG_AILDELETE 0x00000004
- XFS_PTAG_ERROR_REPORT 0x00000008
- XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010
- XFS_PTAG_SHUTDOWN_IOERROR 0x00000020
- XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040
-
- This option is intended for debugging only.
-
- fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1)
- Controls whether symlinks are created with mode 0777 (default)
- or whether their mode is affected by the umask (irix mode).
-
- fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1)
- Controls files created in SGID directories.
- If the group ID of the new file does not match the effective group
- ID or one of the supplementary group IDs of the parent dir, the
- ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
- is set.
-
- fs.xfs.inherit_sync (Min: 0 Default: 1 Max: 1)
- Setting this to "1" will cause the "sync" flag set
- by the xfs_io(8) chattr command on a directory to be
- inherited by files in that directory.
-
- fs.xfs.inherit_nodump (Min: 0 Default: 1 Max: 1)
- Setting this to "1" will cause the "nodump" flag set
- by the xfs_io(8) chattr command on a directory to be
- inherited by files in that directory.
-
- fs.xfs.inherit_noatime (Min: 0 Default: 1 Max: 1)
- Setting this to "1" will cause the "noatime" flag set
- by the xfs_io(8) chattr command on a directory to be
- inherited by files in that directory.
-
- fs.xfs.inherit_nosymlinks (Min: 0 Default: 1 Max: 1)
- Setting this to "1" will cause the "nosymlinks" flag set
- by the xfs_io(8) chattr command on a directory to be
- inherited by files in that directory.
-
- fs.xfs.rotorstep (Min: 1 Default: 1 Max: 256)
- In "inode32" allocation mode, this option determines how many
- files the allocator attempts to allocate in the same allocation
- group before moving to the next allocation group. The intent
- is to control the rate at which the allocator moves between
- allocation groups when allocating extents for new files.