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e84661aa84
Now that we have reliably tracking of deleted extents in a transaction we can easily implement "online" discard support which calls blkdev_issue_discard once a transaction commits. The actual discard is a two stage operation as we first have to mark the busy extent as not available for reuse before we can start the actual discard. Note that we don't bother supporting discard for the non-delaylog mode. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alex Elder <aelder@sgi.com>
253 lines
10 KiB
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253 lines
10 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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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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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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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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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. This option is incompatible with the nodelaylog option.
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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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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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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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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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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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provided for backwards compatibility, but causes problems for
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backup applications that cannot handle large inode numbers.
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largeio/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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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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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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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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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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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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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 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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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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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.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.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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