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diff --git a/Documentation/filesystems/xfs.txt b/Documentation/filesystems/xfs.txt new file mode 100644 index 0000000..c7d5d0c --- /dev/null +++ b/Documentation/filesystems/xfs.txt @@ -0,0 +1,188 @@ + +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. + + biosize=size + Sets the preferred buffered I/O size (default size is 64K). + "size" must be expressed as the logarithm (base2) of the + desired I/O size. + Valid values for this option are 14 through 16, inclusive + (i.e. 16K, 32K, and 64K bytes). On machines with a 4K + pagesize, 13 (8K bytes) is also a valid size. + The preferred buffered I/O size can also be altered on an + individual file basis using the ioctl(2) system call. + + ikeep/noikeep + When inode clusters are emptied of inodes, keep them around + on the disk (ikeep) - this is the traditional XFS behaviour + and is still the default for now. Using the noikeep option, + inode clusters are returned to the free space pool. + + 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 64K, 4 buffers for filesystems with a blocksize + of 32K, 3 buffers for filesystems with a blocksize of 16K + 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 32MB 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. + + 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. + + osyncisosync + Make O_SYNC writes implement true O_SYNC. WITHOUT this option, + Linux XFS behaves as if an "osyncisdsync" option is used, + which will make writes to files opened with the O_SYNC flag set + behave as if the O_DSYNC flag had been used instead. + This can result in better performance without compromising + data safety. + However if this option is not in effect, timestamp updates from + O_SYNC writes can be lost if the system crashes. + If timestamp updates are critical, use the osyncisosync option. + + quota/usrquota/uqnoenforce + User disk quota accounting enabled, and limits (optionally) + enforced. + + grpquota/gqnoenforce + Group disk quota accounting enabled and limits (optionally) + enforced. + + 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. + +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.restrict_chown (Min: 0 Default: 1 Max: 1) + Controls whether unprivileged users can use chown to "give away" + a file to another user. + + fs.xfs.inherit_sync (Min: 0 Default: 1 Max 1) + Setting this to "1" will cause the "sync" flag set + by the chattr(1) 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 chattr(1) 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 chattr(1) command on a directory to be + inherited by files in that directory. |
