| |
| 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. |
| |
| 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 |
| Sets the number of hash buckets available for hashing the |
| in-memory inodes of the specified mount point. If a value |
| of zero is used, the value selected by the default algorithm |
| will be displayed in /proc/mounts. |
| |
| 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. |
| |
| 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 |
| provided for backwards compatibility, but causes problems for |
| backup 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. |
| |
| 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. |
| |
| 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.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 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. |