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: 6000) 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: 30000) 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.refcache_size (Min: 0 Default: 128 Max: 512) Controls the size of the NFS refcache, which holds references on files opened via NFS to improve performance. The value is the maximum number of files which can be in the cache at any one time. fs.xfs.refcache_purge (Min: 0 Default: 32 Max: 512) Controls the number of entries purged from the NFS refcache every sync interval. 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.