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diff --git a/Documentation/filesystems/xfs.txt b/Documentation/filesystems/xfs.txt new file mode 100644 index 00000000..3e4b3dd1 --- /dev/null +++ b/Documentation/filesystems/xfs.txt @@ -0,0 +1,259 @@ + +The SGI XFS Filesystem +====================== + +XFS is a high performance journaling filesystem which originated +on the SGI IRIX platform. It is completely multi-threaded, can +support large files and large filesystems, extended attributes, +variable block sizes, is extent based, and makes extensive use of +Btrees (directories, extents, free space) to aid both performance +and scalability. + +Refer to the documentation at http://oss.sgi.com/projects/xfs/ +for further details. This implementation is on-disk compatible +with the IRIX version of XFS. + + +Mount Options +============= + +When mounting an XFS filesystem, the following options are accepted. + + allocsize=size + Sets the buffered I/O end-of-file preallocation size when + doing delayed allocation writeout (default size is 64KiB). + Valid values for this option are page size (typically 4KiB) + through to 1GiB, inclusive, in power-of-2 increments. + + attr2/noattr2 + The options enable/disable (default is disabled for backward + compatibility on-disk) an "opportunistic" improvement to be + made in the way inline extended attributes are stored on-disk. + When the new form is used for the first time (by setting or + removing extended attributes) the on-disk superblock feature + bit field will be updated to reflect this format being in use. + + barrier + Enables the use of block layer write barriers for writes into + the journal and unwritten extent conversion. This allows for + drive level write caching to be enabled, for devices that + support write barriers. + + discard + Issue command to let the block device reclaim space freed by the + filesystem. This is useful for SSD devices, thinly provisioned + LUNs and virtual machine images, but may have a performance + impact. + + dmapi + Enable the DMAPI (Data Management API) event callouts. + Use with the "mtpt" option. + + grpid/bsdgroups and nogrpid/sysvgroups + These options define what group ID a newly created file gets. + When grpid is set, it takes the group ID of the directory in + which it is created; otherwise (the default) it takes the fsgid + of the current process, unless the directory has the setgid bit + set, in which case it takes the gid from the parent directory, + and also gets the setgid bit set if it is a directory itself. + + ihashsize=value + In memory inode hashes have been removed, so this option has + no function as of August 2007. Option is deprecated. + + ikeep/noikeep + When ikeep is specified, XFS does not delete empty inode clusters + and keeps them around on disk. ikeep is the traditional XFS + behaviour. When noikeep is specified, empty inode clusters + are returned to the free space pool. The default is noikeep for + non-DMAPI mounts, while ikeep is the default when DMAPI is in use. + + inode64 + Indicates that XFS is allowed to create inodes at any location + in the filesystem, including those which will result in inode + numbers occupying more than 32 bits of significance. This is + the default allocation option. Applications which do not handle + inode numbers bigger than 32 bits, should use inode32 option. + + inode32 + Indicates that XFS is limited to create inodes at locations which + will not result in inode numbers with more than 32 bits of + significance. This is provided for backwards compatibility, since + 64 bits inode numbers might cause problems for some applications + that cannot handle large inode numbers. + + largeio/nolargeio + If "nolargeio" is specified, the optimal I/O reported in + st_blksize by stat(2) will be as small as possible to allow user + applications to avoid inefficient read/modify/write I/O. + If "largeio" specified, a filesystem that has a "swidth" specified + will return the "swidth" value (in bytes) in st_blksize. If the + filesystem does not have a "swidth" specified but does specify + an "allocsize" then "allocsize" (in bytes) will be returned + instead. + If neither of these two options are specified, then filesystem + will behave as if "nolargeio" was specified. + + logbufs=value + Set the number of in-memory log buffers. Valid numbers range + from 2-8 inclusive. + The default value is 8 buffers for filesystems with a + blocksize of 64KiB, 4 buffers for filesystems with a blocksize + of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB + and 2 buffers for all other configurations. Increasing the + number of buffers may increase performance on some workloads + at the cost of the memory used for the additional log buffers + and their associated control structures. + + logbsize=value + Set the size of each in-memory log buffer. + Size may be specified in bytes, or in kilobytes with a "k" suffix. + Valid sizes for version 1 and version 2 logs are 16384 (16k) and + 32768 (32k). Valid sizes for version 2 logs also include + 65536 (64k), 131072 (128k) and 262144 (256k). + The default value for machines with more than 32MiB of memory + is 32768, machines with less memory use 16384 by default. + + logdev=device and rtdev=device + Use an external log (metadata journal) and/or real-time device. + An XFS filesystem has up to three parts: a data section, a log + section, and a real-time section. The real-time section is + optional, and the log section can be separate from the data + section or contained within it. + + mtpt=mountpoint + Use with the "dmapi" option. The value specified here will be + included in the DMAPI mount event, and should be the path of + the actual mountpoint that is used. + + noalign + Data allocations will not be aligned at stripe unit boundaries. + + noatime + Access timestamps are not updated when a file is read. + + norecovery + The filesystem will be mounted without running log recovery. + If the filesystem was not cleanly unmounted, it is likely to + be inconsistent when mounted in "norecovery" mode. + Some files or directories may not be accessible because of this. + Filesystems mounted "norecovery" must be mounted read-only or + the mount will fail. + + nouuid + Don't check for double mounted file systems using the file system uuid. + This is useful to mount LVM snapshot volumes. + + uquota/usrquota/uqnoenforce/quota + User disk quota accounting enabled, and limits (optionally) + enforced. Refer to xfs_quota(8) for further details. + + gquota/grpquota/gqnoenforce + Group disk quota accounting enabled and limits (optionally) + enforced. Refer to xfs_quota(8) for further details. + + pquota/prjquota/pqnoenforce + Project disk quota accounting enabled and limits (optionally) + enforced. Refer to xfs_quota(8) for further details. + + sunit=value and swidth=value + Used to specify the stripe unit and width for a RAID device or + a stripe volume. "value" must be specified in 512-byte block + units. + If this option is not specified and the filesystem was made on + a stripe volume or the stripe width or unit were specified for + the RAID device at mkfs time, then the mount system call will + restore the value from the superblock. For filesystems that + are made directly on RAID devices, these options can be used + to override the information in the superblock if the underlying + disk layout changes after the filesystem has been created. + The "swidth" option is required if the "sunit" option has been + specified, and must be a multiple of the "sunit" value. + + swalloc + Data allocations will be rounded up to stripe width boundaries + when the current end of file is being extended and the file + size is larger than the stripe width size. + + +sysctls +======= + +The following sysctls are available for the XFS filesystem: + + fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1) + Setting this to "1" clears accumulated XFS statistics + in /proc/fs/xfs/stat. It then immediately resets to "0". + + fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000) + The interval at which the xfssyncd thread flushes metadata + out to disk. This thread will flush log activity out, and + do some processing on unlinked inodes. + + fs.xfs.xfsbufd_centisecs (Min: 50 Default: 100 Max: 3000) + The interval at which xfsbufd scans the dirty metadata buffers list. + + fs.xfs.age_buffer_centisecs (Min: 100 Default: 1500 Max: 720000) + The age at which xfsbufd flushes dirty metadata buffers to disk. + + fs.xfs.error_level (Min: 0 Default: 3 Max: 11) + A volume knob for error reporting when internal errors occur. + This will generate detailed messages & backtraces for filesystem + shutdowns, for example. Current threshold values are: + + XFS_ERRLEVEL_OFF: 0 + XFS_ERRLEVEL_LOW: 1 + XFS_ERRLEVEL_HIGH: 5 + + fs.xfs.panic_mask (Min: 0 Default: 0 Max: 127) + Causes certain error conditions to call BUG(). Value is a bitmask; + AND together the tags which represent errors which should cause panics: + + XFS_NO_PTAG 0 + XFS_PTAG_IFLUSH 0x00000001 + XFS_PTAG_LOGRES 0x00000002 + XFS_PTAG_AILDELETE 0x00000004 + XFS_PTAG_ERROR_REPORT 0x00000008 + XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010 + XFS_PTAG_SHUTDOWN_IOERROR 0x00000020 + XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040 + + This option is intended for debugging only. + + fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1) + Controls whether symlinks are created with mode 0777 (default) + or whether their mode is affected by the umask (irix mode). + + fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1) + Controls files created in SGID directories. + If the group ID of the new file does not match the effective group + ID or one of the supplementary group IDs of the parent dir, the + ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl + is set. + + fs.xfs.inherit_sync (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "sync" flag set + by the xfs_io(8) chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_nodump (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "nodump" flag set + by the xfs_io(8) chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_noatime (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "noatime" flag set + by the xfs_io(8) chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_nosymlinks (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "nosymlinks" flag set + by the xfs_io(8) chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.rotorstep (Min: 1 Default: 1 Max: 256) + In "inode32" allocation mode, this option determines how many + files the allocator attempts to allocate in the same allocation + group before moving to the next allocation group. The intent + is to control the rate at which the allocator moves between + allocation groups when allocating extents for new files. |