470 lines
17 KiB
Plaintext
470 lines
17 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 https://xfs.wiki.kernel.org/
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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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For boolean mount options, the names with the (*) suffix is the
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default behaviour.
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allocsize=size
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Sets the buffered I/O end-of-file preallocation size when
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doing delayed allocation writeout (default size is 64KiB).
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Valid values for this option are page size (typically 4KiB)
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through to 1GiB, inclusive, in power-of-2 increments.
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The default behaviour is for dynamic end-of-file
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preallocation size, which uses a set of heuristics to
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optimise the preallocation size based on the current
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allocation patterns within the file and the access patterns
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to the file. Specifying a fixed allocsize value turns off
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the dynamic behaviour.
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attr2
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noattr2
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The options enable/disable an "opportunistic" improvement to
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be made in the way inline extended attributes are stored
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on-disk. When the new form is used for the first time when
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attr2 is selected (either when setting or removing extended
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attributes) the on-disk superblock feature bit field will be
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updated to reflect this format being in use.
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The default behaviour is determined by the on-disk feature
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bit indicating that attr2 behaviour is active. If either
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mount option it set, then that becomes the new default used
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by the filesystem.
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CRC enabled filesystems always use the attr2 format, and so
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will reject the noattr2 mount option if it is set.
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discard
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nodiscard (*)
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Enable/disable the issuing of commands to let the block
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device reclaim space freed by the filesystem. This is
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useful for SSD devices, thinly provisioned LUNs and virtual
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machine images, but may have a performance impact.
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Note: It is currently recommended that you use the fstrim
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application to discard unused blocks rather than the discard
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mount option because the performance impact of this option
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is quite severe.
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grpid/bsdgroups
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nogrpid/sysvgroups (*)
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These options define what group ID a newly created file
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gets. When grpid is set, it takes the group ID of the
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directory in which it is created; otherwise it takes the
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fsgid of the current process, unless the directory has the
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setgid bit set, in which case it takes the gid from the
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parent directory, and also gets the setgid bit set if it is
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a directory itself.
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filestreams
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Make the data allocator use the filestreams allocation mode
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across the entire filesystem rather than just on directories
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configured to use it.
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ikeep
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noikeep (*)
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When ikeep is specified, XFS does not delete empty inode
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clusters and keeps them around on disk. When noikeep is
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specified, empty inode clusters are returned to the free
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space pool.
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inode32
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inode64 (*)
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When inode32 is specified, it indicates that XFS limits
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inode creation to locations which will not result in inode
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numbers with more than 32 bits of significance.
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When inode64 is specified, it indicates that XFS is allowed
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to create inodes at any location in the filesystem,
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including those which will result in inode numbers occupying
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more than 32 bits of significance.
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inode32 is provided for backwards compatibility with older
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systems and applications, since 64 bits inode numbers might
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cause problems for some applications that cannot handle
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large inode numbers. If applications are in use which do
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not handle inode numbers bigger than 32 bits, the inode32
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option should be specified.
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largeio
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nolargeio (*)
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If "nolargeio" is specified, the optimal I/O reported in
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st_blksize by stat(2) will be as small as possible to allow
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user applications to avoid inefficient read/modify/write
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I/O. This is typically the page size of the machine, as
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this is the granularity of the page cache.
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If "largeio" specified, a filesystem that was created with a
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"swidth" specified will return the "swidth" value (in bytes)
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in st_blksize. If the filesystem does not have a "swidth"
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specified but does specify an "allocsize" then "allocsize"
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(in bytes) will be returned instead. Otherwise the behaviour
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is the same as if "nolargeio" was specified.
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logbufs=value
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Set the number of in-memory log buffers. Valid numbers
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range from 2-8 inclusive.
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The default value is 8 buffers.
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If the memory cost of 8 log buffers is too high on small
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systems, then it may be reduced at some cost to performance
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on metadata intensive workloads. The logbsize option below
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controls the size of each buffer and so is also relevant to
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this case.
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logbsize=value
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Set the size of each in-memory log buffer. The size may be
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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)
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and 32768 (32k). Valid sizes for version 2 logs also
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include 65536 (64k), 131072 (128k) and 262144 (256k). The
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logbsize must be an integer multiple of the log
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stripe unit configured at mkfs time.
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The default value for for version 1 logs is 32768, while the
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default value for version 2 logs is MAX(32768, log_sunit).
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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
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boundaries. This is only relevant to filesystems created
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with non-zero data alignment parameters (sunit, swidth) by
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mkfs.
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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
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system uuid. This is useful to mount LVM snapshot volumes,
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and often used in combination with "norecovery" for mounting
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read-only snapshots.
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noquota
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Forcibly turns off all quota accounting and enforcement
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within the filesystem.
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uquota/usrquota/uqnoenforce/quota
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User disk quota accounting enabled, and limits (optionally)
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enforced. Refer to xfs_quota(8) for further details.
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gquota/grpquota/gqnoenforce
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Group disk quota accounting enabled and limits (optionally)
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enforced. Refer to xfs_quota(8) for further details.
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pquota/prjquota/pqnoenforce
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Project disk quota accounting enabled and limits (optionally)
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enforced. Refer to xfs_quota(8) for further details.
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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
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or a stripe volume. "value" must be specified in 512-byte
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block units. These options are only relevant to filesystems
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that were created with non-zero data alignment parameters.
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The sunit and swidth parameters specified must be compatible
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with the existing filesystem alignment characteristics. In
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general, that means the only valid changes to sunit are
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increasing it by a power-of-2 multiple. Valid swidth values
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are any integer multiple of a valid sunit value.
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Typically the only time these mount options are necessary if
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after an underlying RAID device has had it's geometry
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modified, such as adding a new disk to a RAID5 lun and
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reshaping it.
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swalloc
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Data allocations will be rounded up to stripe width boundaries
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when the current end of file is being extended and the file
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size is larger than the stripe width size.
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wsync
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When specified, all filesystem namespace operations are
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executed synchronously. This ensures that when the namespace
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operation (create, unlink, etc) completes, the change to the
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namespace is on stable storage. This is useful in HA setups
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where failover must not result in clients seeing
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inconsistent namespace presentation during or after a
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failover event.
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Deprecated Mount Options
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========================
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Name Removal Schedule
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---- ----------------
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barrier no earlier than v4.15
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nobarrier no earlier than v4.15
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Removed Mount Options
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=====================
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Name Removed
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---- -------
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delaylog/nodelaylog v4.0
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ihashsize v4.0
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irixsgid v4.0
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osyncisdsync/osyncisosync v4.0
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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 filesystem flushes metadata
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out to disk and runs internal cache cleanup routines.
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fs.xfs.filestream_centisecs (Min: 1 Default: 3000 Max: 360000)
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The interval at which the filesystem ages filestreams cache
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references and returns timed-out AGs back to the free stream
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pool.
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fs.xfs.speculative_prealloc_lifetime
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(Units: seconds Min: 1 Default: 300 Max: 86400)
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The interval at which the background scanning for inodes
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with unused speculative preallocation runs. The scan
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removes unused preallocation from clean inodes and releases
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the unused space back to the free pool.
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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: 255)
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Causes certain error conditions to call BUG(). Value is a bitmask;
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OR 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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XFS_PTAG_FSBLOCK_ZERO 0x00000080
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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.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 xfs_io(8) chattr 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 xfs_io(8) chattr 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 xfs_io(8) chattr command on a directory to be
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inherited by files in that directory.
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fs.xfs.inherit_nosymlinks (Min: 0 Default: 1 Max: 1)
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Setting this to "1" will cause the "nosymlinks" flag set
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by the xfs_io(8) chattr command on a directory to be
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inherited by files in that directory.
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fs.xfs.inherit_nodefrag (Min: 0 Default: 1 Max: 1)
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Setting this to "1" will cause the "nodefrag" flag set
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by the xfs_io(8) chattr command on a directory to be
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inherited by files in that directory.
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fs.xfs.rotorstep (Min: 1 Default: 1 Max: 256)
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In "inode32" allocation mode, this option determines how many
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files the allocator attempts to allocate in the same allocation
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group before moving to the next allocation group. The intent
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is to control the rate at which the allocator moves between
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allocation groups when allocating extents for new files.
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Deprecated Sysctls
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==================
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None at present.
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Removed Sysctls
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===============
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Name Removed
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---- -------
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fs.xfs.xfsbufd_centisec v4.0
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fs.xfs.age_buffer_centisecs v4.0
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Error handling
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==============
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XFS can act differently according to the type of error found during its
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operation. The implementation introduces the following concepts to the error
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handler:
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-failure speed:
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Defines how fast XFS should propagate an error upwards when a specific
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error is found during the filesystem operation. It can propagate
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immediately, after a defined number of retries, after a set time period,
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or simply retry forever.
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-error classes:
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Specifies the subsystem the error configuration will apply to, such as
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metadata IO or memory allocation. Different subsystems will have
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different error handlers for which behaviour can be configured.
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-error handlers:
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Defines the behavior for a specific error.
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The filesystem behavior during an error can be set via sysfs files. Each
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error handler works independently - the first condition met by an error handler
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for a specific class will cause the error to be propagated rather than reset and
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retried.
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The action taken by the filesystem when the error is propagated is context
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dependent - it may cause a shut down in the case of an unrecoverable error,
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it may be reported back to userspace, or it may even be ignored because
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there's nothing useful we can with the error or anyone we can report it to (e.g.
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during unmount).
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The configuration files are organized into the following hierarchy for each
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mounted filesystem:
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/sys/fs/xfs/<dev>/error/<class>/<error>/
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Where:
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<dev>
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The short device name of the mounted filesystem. This is the same device
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name that shows up in XFS kernel error messages as "XFS(<dev>): ..."
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<class>
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The subsystem the error configuration belongs to. As of 4.9, the defined
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classes are:
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- "metadata": applies metadata buffer write IO
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<error>
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The individual error handler configurations.
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Each filesystem has "global" error configuration options defined in their top
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level directory:
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/sys/fs/xfs/<dev>/error/
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fail_at_unmount (Min: 0 Default: 1 Max: 1)
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Defines the filesystem error behavior at unmount time.
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If set to a value of 1, XFS will override all other error configurations
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during unmount and replace them with "immediate fail" characteristics.
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i.e. no retries, no retry timeout. This will always allow unmount to
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succeed when there are persistent errors present.
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If set to 0, the configured retry behaviour will continue until all
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retries and/or timeouts have been exhausted. This will delay unmount
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completion when there are persistent errors, and it may prevent the
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filesystem from ever unmounting fully in the case of "retry forever"
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handler configurations.
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Note: there is no guarantee that fail_at_unmount can be set whilst an
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unmount is in progress. It is possible that the sysfs entries are
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removed by the unmounting filesystem before a "retry forever" error
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handler configuration causes unmount to hang, and hence the filesystem
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must be configured appropriately before unmount begins to prevent
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unmount hangs.
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Each filesystem has specific error class handlers that define the error
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propagation behaviour for specific errors. There is also a "default" error
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handler defined, which defines the behaviour for all errors that don't have
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specific handlers defined. Where multiple retry constraints are configuredi for
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a single error, the first retry configuration that expires will cause the error
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to be propagated. The handler configurations are found in the directory:
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/sys/fs/xfs/<dev>/error/<class>/<error>/
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max_retries (Min: -1 Default: Varies Max: INTMAX)
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Defines the allowed number of retries of a specific error before
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the filesystem will propagate the error. The retry count for a given
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error context (e.g. a specific metadata buffer) is reset every time
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there is a successful completion of the operation.
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Setting the value to "-1" will cause XFS to retry forever for this
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specific error.
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Setting the value to "0" will cause XFS to fail immediately when the
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specific error is reported.
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Setting the value to "N" (where 0 < N < Max) will make XFS retry the
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operation "N" times before propagating the error.
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retry_timeout_seconds (Min: -1 Default: Varies Max: 1 day)
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Define the amount of time (in seconds) that the filesystem is
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allowed to retry its operations when the specific error is
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found.
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Setting the value to "-1" will allow XFS to retry forever for this
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specific error.
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Setting the value to "0" will cause XFS to fail immediately when the
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specific error is reported.
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Setting the value to "N" (where 0 < N < Max) will allow XFS to retry the
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operation for up to "N" seconds before propagating the error.
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Note: The default behaviour for a specific error handler is dependent on both
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the class and error context. For example, the default values for
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"metadata/ENODEV" are "0" rather than "-1" so that this error handler defaults
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to "fail immediately" behaviour. This is done because ENODEV is a fatal,
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unrecoverable error no matter how many times the metadata IO is retried.
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