189 lines
7.4 KiB
Plaintext
189 lines
7.4 KiB
Plaintext
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The SGI XFS Filesystem
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======================
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XFS is a high performance journaling filesystem which originated
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on the SGI IRIX platform. It is completely multi-threaded, can
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support large files and large filesystems, extended attributes,
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variable block sizes, is extent based, and makes extensive use of
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Btrees (directories, extents, free space) to aid both performance
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and scalability.
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Refer to the documentation at http://oss.sgi.com/projects/xfs/
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for further details. This implementation is on-disk compatible
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with the IRIX version of XFS.
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Mount Options
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=============
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When mounting an XFS filesystem, the following options are accepted.
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biosize=size
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Sets the preferred buffered I/O size (default size is 64K).
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"size" must be expressed as the logarithm (base2) of the
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desired I/O size.
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Valid values for this option are 14 through 16, inclusive
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(i.e. 16K, 32K, and 64K bytes). On machines with a 4K
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pagesize, 13 (8K bytes) is also a valid size.
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The preferred buffered I/O size can also be altered on an
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individual file basis using the ioctl(2) system call.
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ikeep/noikeep
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When inode clusters are emptied of inodes, keep them around
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on the disk (ikeep) - this is the traditional XFS behaviour
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and is still the default for now. Using the noikeep option,
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inode clusters are returned to the free space pool.
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logbufs=value
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Set the number of in-memory log buffers. Valid numbers range
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from 2-8 inclusive.
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The default value is 8 buffers for filesystems with a
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blocksize of 64K, 4 buffers for filesystems with a blocksize
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of 32K, 3 buffers for filesystems with a blocksize of 16K
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and 2 buffers for all other configurations. Increasing the
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number of buffers may increase performance on some workloads
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at the cost of the memory used for the additional log buffers
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and their associated control structures.
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logbsize=value
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Set the size of each in-memory log buffer.
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Size may be specified in bytes, or in kilobytes with a "k" suffix.
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Valid sizes for version 1 and version 2 logs are 16384 (16k) and
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32768 (32k). Valid sizes for version 2 logs also include
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65536 (64k), 131072 (128k) and 262144 (256k).
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The default value for machines with more than 32MB of memory
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is 32768, machines with less memory use 16384 by default.
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logdev=device and rtdev=device
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Use an external log (metadata journal) and/or real-time device.
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An XFS filesystem has up to three parts: a data section, a log
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section, and a real-time section. The real-time section is
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optional, and the log section can be separate from the data
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section or contained within it.
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noalign
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Data allocations will not be aligned at stripe unit boundaries.
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noatime
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Access timestamps are not updated when a file is read.
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norecovery
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The filesystem will be mounted without running log recovery.
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If the filesystem was not cleanly unmounted, it is likely to
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be inconsistent when mounted in "norecovery" mode.
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Some files or directories may not be accessible because of this.
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Filesystems mounted "norecovery" must be mounted read-only or
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the mount will fail.
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nouuid
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Don't check for double mounted file systems using the file system uuid.
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This is useful to mount LVM snapshot volumes.
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osyncisosync
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Make O_SYNC writes implement true O_SYNC. WITHOUT this option,
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Linux XFS behaves as if an "osyncisdsync" option is used,
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which will make writes to files opened with the O_SYNC flag set
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behave as if the O_DSYNC flag had been used instead.
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This can result in better performance without compromising
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data safety.
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However if this option is not in effect, timestamp updates from
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O_SYNC writes can be lost if the system crashes.
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If timestamp updates are critical, use the osyncisosync option.
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quota/usrquota/uqnoenforce
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User disk quota accounting enabled, and limits (optionally)
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enforced.
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grpquota/gqnoenforce
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Group disk quota accounting enabled and limits (optionally)
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enforced.
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sunit=value and swidth=value
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Used to specify the stripe unit and width for a RAID device or
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a stripe volume. "value" must be specified in 512-byte block
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units.
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If this option is not specified and the filesystem was made on
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a stripe volume or the stripe width or unit were specified for
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the RAID device at mkfs time, then the mount system call will
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restore the value from the superblock. For filesystems that
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are made directly on RAID devices, these options can be used
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to override the information in the superblock if the underlying
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disk layout changes after the filesystem has been created.
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The "swidth" option is required if the "sunit" option has been
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specified, and must be a multiple of the "sunit" value.
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sysctls
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=======
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The following sysctls are available for the XFS filesystem:
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fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1)
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Setting this to "1" clears accumulated XFS statistics
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in /proc/fs/xfs/stat. It then immediately resets to "0".
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fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000)
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The interval at which the xfssyncd thread flushes metadata
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out to disk. This thread will flush log activity out, and
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do some processing on unlinked inodes.
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fs.xfs.xfsbufd_centisecs (Min: 50 Default: 100 Max: 3000)
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The interval at which xfsbufd scans the dirty metadata buffers list.
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fs.xfs.age_buffer_centisecs (Min: 100 Default: 1500 Max: 720000)
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The age at which xfsbufd flushes dirty metadata buffers to disk.
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fs.xfs.error_level (Min: 0 Default: 3 Max: 11)
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A volume knob for error reporting when internal errors occur.
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This will generate detailed messages & backtraces for filesystem
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shutdowns, for example. Current threshold values are:
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XFS_ERRLEVEL_OFF: 0
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XFS_ERRLEVEL_LOW: 1
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XFS_ERRLEVEL_HIGH: 5
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fs.xfs.panic_mask (Min: 0 Default: 0 Max: 127)
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Causes certain error conditions to call BUG(). Value is a bitmask;
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AND together the tags which represent errors which should cause panics:
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XFS_NO_PTAG 0
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XFS_PTAG_IFLUSH 0x00000001
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XFS_PTAG_LOGRES 0x00000002
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XFS_PTAG_AILDELETE 0x00000004
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XFS_PTAG_ERROR_REPORT 0x00000008
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XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010
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XFS_PTAG_SHUTDOWN_IOERROR 0x00000020
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XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040
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This option is intended for debugging only.
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fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1)
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Controls whether symlinks are created with mode 0777 (default)
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or whether their mode is affected by the umask (irix mode).
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fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1)
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Controls files created in SGID directories.
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If the group ID of the new file does not match the effective group
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ID or one of the supplementary group IDs of the parent dir, the
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ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
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is set.
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fs.xfs.restrict_chown (Min: 0 Default: 1 Max: 1)
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Controls whether unprivileged users can use chown to "give away"
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a file to another user.
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fs.xfs.inherit_sync (Min: 0 Default: 1 Max 1)
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Setting this to "1" will cause the "sync" flag set
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by the chattr(1) command on a directory to be
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inherited by files in that directory.
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fs.xfs.inherit_nodump (Min: 0 Default: 1 Max 1)
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Setting this to "1" will cause the "nodump" flag set
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by the chattr(1) command on a directory to be
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inherited by files in that directory.
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fs.xfs.inherit_noatime (Min: 0 Default: 1 Max 1)
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Setting this to "1" will cause the "noatime" flag set
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by the chattr(1) command on a directory to be
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inherited by files in that directory.
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