| |
| 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. |
| |
| |
| 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. |
| |
| 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. |
| |
| 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. |
| |
| nouuid |
| Don't check for double mounted file systems using the file system uuid. |
| This is useful to mount LVM snapshot volumes. |
| |