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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.
+ biosize=size
+ Sets the preferred buffered I/O size (default size is 64K).
+ "size" must be expressed as the logarithm (base2) of the
+ desired I/O size.
+ Valid values for this option are 14 through 16, inclusive
+ (i.e. 16K, 32K, and 64K bytes). On machines with a 4K
+ pagesize, 13 (8K bytes) is also a valid size.
+ The preferred buffered I/O size can also be altered on an
+ individual file basis using the ioctl(2) system call.
+ ikeep/noikeep
+ When inode clusters are emptied of inodes, keep them around
+ on the disk (ikeep) - this is the traditional XFS behaviour
+ and is still the default for now. Using the noikeep option,
+ inode clusters are returned to the free space pool.
+ 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 64K, 4 buffers for filesystems with a blocksize
+ of 32K, 3 buffers for filesystems with a blocksize of 16K
+ 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 32MB 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.
+ 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.
+ osyncisosync
+ Make O_SYNC writes implement true O_SYNC. WITHOUT this option,
+ Linux XFS behaves as if an "osyncisdsync" option is used,
+ which will make writes to files opened with the O_SYNC flag set
+ behave as if the O_DSYNC flag had been used instead.
+ This can result in better performance without compromising
+ data safety.
+ However if this option is not in effect, timestamp updates from
+ O_SYNC writes can be lost if the system crashes.
+ If timestamp updates are critical, use the osyncisosync option.
+ quota/usrquota/uqnoenforce
+ User disk quota accounting enabled, and limits (optionally)
+ enforced.
+ grpquota/gqnoenforce
+ Group disk quota accounting enabled and limits (optionally)
+ enforced.
+ 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.
+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:
+ 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_PTAG_IFLUSH 0x00000001
+ XFS_PTAG_LOGRES 0x00000002
+ 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.restrict_chown (Min: 0 Default: 1 Max: 1)
+ Controls whether unprivileged users can use chown to "give away"
+ a file to another user.
+ fs.xfs.inherit_sync (Min: 0 Default: 1 Max 1)
+ Setting this to "1" will cause the "sync" flag set
+ by the chattr(1) 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 chattr(1) 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 chattr(1) command on a directory to be
+ inherited by files in that directory.