|xfs(5)||File Formats Manual||xfs(5)|
mkfs.xfs(8) options, the realtime section is absent, and the log area is contained within the data section. The log section can be either separate from the data section or contained within it. The filesystem sections are divided into a certain number of blocks, whose size is specified at mkfs.xfs(8) time with the -b option. The data section contains all the filesystem metadata (inodes, directories, indirect blocks) as well as the user file data for ordinary (non-realtime) files and the log area if the log is internal to the data section. The data section is divided into a number of allocation groups. The number and size of the allocation groups are chosen by mkfs.xfs(8) so that there is normally a small number of equal-sized groups. The number of allocation groups controls the amount of parallelism available in file and block allocation. It should be increased from the default if there is sufficient memory and a lot of allocation activity. The number of allocation groups should not be set very high, since this can cause large amounts of CPU time to be used by the filesystem, especially when the filesystem is nearly full. More allocation groups are added (of the original size) when xfs_growfs(8) is run. The log section (or area, if it is internal to the data section) is used to store changes to filesystem metadata while the filesystem is running until those changes are made to the data section. It is written sequentially during normal operation and read only during mount. When mounting a filesystem after a crash, the log is read to complete operations that were in progress at the time of the crash. The realtime section is used to store the data of realtime files. These files had an attribute bit set through xfsctl(3) after file creation, before any data was written to the file. The realtime section is divided into a number of extents of fixed size (specified at mkfs.xfs(8) time). Each file in the realtime section has an extent size that is a multiple of the realtime section extent size. Each allocation group contains several data structures. The first sector contains the superblock. For allocation groups after the first, the superblock is just a copy and is not updated after mkfs.xfs(8). The next three sectors contain information for block and inode allocation within the allocation group. Also contained within each allocation group are data structures to locate free blocks and inodes; these are located through the header structures. Each XFS filesystem is labeled with a Universal Unique Identifier (UUID). The UUID is stored in every allocation group header and is used to help distinguish one XFS filesystem from another, therefore you should avoid using dd(1) or other block-by-block copying programs to copy XFS filesystems. If two XFS filesystems on the same machine have the same UUID, xfsdump(8) may become confused when doing incremental and resumed dumps. xfsdump(8) and xfsrestore(8) are recommended for making copies of XFS filesystems. xfsctl(3) and by-handle (see open_by_handle(3)) interfaces. mount(8) manual page for more details.a - append onlyA - no atime updatesd - no dumpi - immutableS - synchronous updatesFor descriptions of these attribute flags, please refer to the chattr(1) man page. chattr(1), xfsctl(3), mount(8), mkfs.xfs(8), xfs_info(8), xfs_admin(8), xfsdump(8), xfsrestore(8).
- Sets the buffered I/O end-of-file preallocation size when
doing delayed allocation writeout. Valid values for this option are page
size (typically 4KiB) through to 1GiB, inclusive, in power-of-2
- The options enable/disable 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 when attr2 is
selected (either when setting or removing extended attributes) the on-disk
superblock feature bit field will be updated to reflect this format being
- Note: This option has been deprecated as of kernel
v4.10; in that version, integrity operations are always performed and the
mount option is ignored. These mount options will be removed no earlier
than kernel v4.15.
- Enable/disable the issuing of commands 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.
- 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 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.
- Make the data allocator use the filestreams allocation mode across the entire filesystem rather than just on directories configured to use it.
- When ikeep is specified, XFS does not delete empty inode clusters and keeps them around on disk. When noikeep is specified, empty inode clusters are returned to the free space pool. noikeep is the default.
- When inode32 is specified, it indicates that XFS limits
inode creation to locations which will not result in inode numbers with
more than 32 bits of significance.
- 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. This is
typically the page size of the machine, as this is the granularity of the
- Set the number of in-memory log buffers. Valid numbers
range from 2–8 inclusive.
- Set the size of each in-memory log buffer. The size may be
specified in bytes, or in kibibytes (KiB) with a "k" suffix.
Valid sizes for version 1 and version 2 logs are 16384 (value=16k) and
32768 (value=32k). Valid sizes for version 2 logs also include 65536
(value=64k), 131072 (value=128k) and 262144 (value=256k). The logbsize
must be an integer multiple of the log stripe unit configured at mkfs
- 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.
- Data allocations will not be aligned at stripe unit boundaries. This is only relevant to filesystems created with non-zero data alignment parameters (sunit, swidth) by mkfs.
- 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.
- Don't check for double mounted file systems using the file system uuid. This is useful to mount LVM snapshot volumes, and often used in combination with "norecovery" for mounting read-only snapshots.
- Forcibly turns off all quota accounting and enforcement within the filesystem.
- User disk quota accounting enabled, and limits (optionally) enforced. Refer to xfs_quota(8) for further details.
- Group disk quota accounting enabled and limits (optionally) enforced. Refer to xfs_quota(8) for further details.
- 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. These options are only relevant to filesystems that were created
with non-zero data alignment parameters.
- 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.
- When specified, all filesystem namespace operations are executed synchronously. This ensures that when the namespace operation (create, unlink, etc) completes, the change to the namespace is on stable storage. This is useful in HA setups where failover must not result in clients seeing inconsistent namespace presentation during or after a failover event.