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@@ -18,6 +18,8 @@ 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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@@ -25,97 +27,128 @@ When mounting an XFS filesystem, the following options are accepted.
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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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- attr2/noattr2
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- The options enable/disable (default is disabled for backward
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- compatibility on-disk) an "opportunistic" improvement to be
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- made in the way inline extended attributes are stored on-disk.
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- When the new form is used for the first time (by setting or
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- removing extended attributes) the on-disk superblock feature
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- bit field will be updated to reflect this format being in use.
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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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+
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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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+
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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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- barrier
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- Enables the use of block layer write barriers for writes into
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- the journal and unwritten extent conversion. This allows for
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- drive level write caching to be enabled, for devices that
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- support write barriers.
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+ barrier (*)
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+ nobarrier
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+ Enables/disables the use of block layer write barriers for
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+ writes into the journal and for data integrity operations.
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+ This allows for drive level write caching to be enabled, for
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+ devices that support write barriers.
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discard
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- Issue command to let the block device reclaim space freed by the
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- filesystem. This is useful for SSD devices, thinly provisioned
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- LUNs and virtual machine images, but may have a performance
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- impact.
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-
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- dmapi
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- Enable the DMAPI (Data Management API) event callouts.
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- Use with the "mtpt" option.
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-
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- grpid/bsdgroups and nogrpid/sysvgroups
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- These options define what group ID a newly created file gets.
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- When grpid is set, it takes the group ID of the directory in
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- which it is created; otherwise (the default) it takes the fsgid
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- of the current process, unless the directory has the setgid bit
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- set, in which case it takes the gid from the parent directory,
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- and also gets the setgid bit set if it is a directory itself.
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-
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- ihashsize=value
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- In memory inode hashes have been removed, so this option has
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- no function as of August 2007. Option is deprecated.
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-
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- ikeep/noikeep
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- When ikeep is specified, XFS does not delete empty inode clusters
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- and keeps them around on disk. ikeep is the traditional XFS
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- behaviour. When noikeep is specified, empty inode clusters
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- are returned to the free space pool. The default is noikeep for
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- non-DMAPI mounts, while ikeep is the default when DMAPI is in use.
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-
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- inode64
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- Indicates that XFS is allowed to create inodes at any location
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- in the filesystem, including those which will result in inode
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- numbers occupying more than 32 bits of significance. This is
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- the default allocation option. Applications which do not handle
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- inode numbers bigger than 32 bits, should use inode32 option.
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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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+
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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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+
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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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+
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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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+
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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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- Indicates that XFS is limited to create inodes at locations which
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- will not result in inode numbers with more than 32 bits of
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- significance. This is provided for backwards compatibility, since
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- 64 bits inode numbers might cause problems for some applications
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- that cannot handle large inode numbers.
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-
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- largeio/nolargeio
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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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+
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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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+
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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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+
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+
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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 user
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- applications to avoid inefficient read/modify/write I/O.
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- If "largeio" specified, a filesystem that has a "swidth" specified
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- will return the "swidth" value (in bytes) in st_blksize. If the
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- filesystem does not have a "swidth" specified but does specify
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- an "allocsize" then "allocsize" (in bytes) will be returned
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- instead.
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- If neither of these two options are specified, then filesystem
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- will behave as if "nolargeio" was specified.
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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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+
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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 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 64KiB, 4 buffers for filesystems with a blocksize
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- of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB
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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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+ Set the number of in-memory log buffers. Valid numbers
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+ range from 2-8 inclusive.
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+
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+ The default value is 8 buffers.
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+
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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 relevent 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.
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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 32MiB of memory
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- is 32768, machines with less memory use 16384 by default.
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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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+
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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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@@ -124,16 +157,11 @@ When mounting an XFS filesystem, the following options are accepted.
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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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- mtpt=mountpoint
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- Use with the "dmapi" option. The value specified here will be
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- included in the DMAPI mount event, and should be the path of
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- the actual mountpoint that is used.
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-
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noalign
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- Data allocations will not be aligned at stripe unit boundaries.
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-
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- noatime
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- Access timestamps are not updated when a file is read.
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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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@@ -144,8 +172,14 @@ When mounting an XFS filesystem, the following options are accepted.
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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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+ 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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+
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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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@@ -160,24 +194,64 @@ When mounting an XFS filesystem, the following options are accepted.
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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 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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+ 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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+
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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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+
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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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+
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+
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+Deprecated Mount Options
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+========================
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+
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+ delaylog/nodelaylog
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+ Delayed logging is the only logging method that XFS supports
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+ now, so these mount options are now ignored.
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+
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+ Due for removal in 3.12.
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+
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+ ihashsize=value
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+ In memory inode hashes have been removed, so this option has
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+ no function as of August 2007. Option is deprecated.
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+
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+ Due for removal in 3.12.
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+
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+ irixsgid
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+ This behaviour is now controlled by a sysctl, so the mount
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+ option is ignored.
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+
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+ Due for removal in 3.12.
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+
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+ osyncisdsync
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+ osyncisosync
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+ O_SYNC and O_DSYNC are fully supported, so there is no need
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+ for these options any more.
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+
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+ Due for removal in 3.12.
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sysctls
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=======
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@@ -189,15 +263,20 @@ The following sysctls are available for the XFS filesystem:
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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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+ 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.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.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.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.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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@@ -254,9 +333,31 @@ The following sysctls are available for the XFS filesystem:
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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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+
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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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+
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+Deprecated Sysctls
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+==================
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+
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+ fs.xfs.xfsbufd_centisecs (Min: 50 Default: 100 Max: 3000)
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+ Dirty metadata is now tracked by the log subsystem and
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+ flushing is driven by log space and idling demands. The
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+ xfsbufd no longer exists, so this syctl does nothing.
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+
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+ Due for removal in 3.14.
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+
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+ fs.xfs.age_buffer_centisecs (Min: 100 Default: 1500 Max: 720000)
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+ Dirty metadata is now tracked by the log subsystem and
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+ flushing is driven by log space and idling demands. The
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+ xfsbufd no longer exists, so this syctl does nothing.
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+
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+ Due for removal in 3.14.
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