# XFS

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- File systems

XFS is a high-performance journaling file system created by Silicon Graphics, Inc. XFS is particularly proficient at parallel IO due to its allocation group based design. This enables extreme scalability of IO threads, filesystem bandwidth, file and filesystem size when spanning multiple storage devices.

## Installation

The tools to manage XFS partions are in the xfsprogs package from the official repositories, which is included in the default base installation.

## Data corruption

If for whatever reason you experience data corruption, you will need to repair the filesystem manually.

### Repair XFS Filesystem

First unmount the XFS filesystem.

    # unmount /dev/sda3

Once unmounted, run the xfs_repair tool.

    # xfs_repair -v /dev/sda3

## Performance

For optimal speed, just create an XFS file system with:

    $ mkfs.xfs /dev/thetargetpartition

Yep, so simple - since all of the "boost knobs" are already "on" by default.

Warning: Disabling barriers, disabling atime, and other performance enhancements make data corruption and failure much more likely.

### Stripe size and width

If this filesystem will be on a striped RAID you can gain significant speed improvements by specifying the stripe size to the `mkfs.xfs` command.

See How to calculate the correct sunit,swidth values for optimal performance

### Disable barrier

You can increase performance by disabling barrier usage for the filesystem by adding the nobarrier mount option to the `/etc/fstab` file.

### Access time

On some filesystems you can increase performance by adding the `noatime` mount option to the `/etc/fstab` file. For XFS filesystems the default atime behaviour is `relatime`, which has almost no overhead compared to noatime but still maintains sane atime values. All Linux filesystems use this as the default now (since around 2.6.30), but XFS has used relatime-like behaviour since 2006, so no-one should really need to ever use noatime on XFS for performance reasons.

Also, `noatime` implies `nodiratime`, so there is never a need to specify nodiratime when noatime is also specified.

### Defragmentation

Although the extent-based nature of XFS and the delayed allocation strategy it uses significantly improves the file system's resistance to fragmentation problems, XFS provides a filesystem defragmentation utility (xfs_fsr, short for XFS filesystem reorganizer) that can defragment the files on a mounted and active XFS filesystem. It can be useful to view XFS fragmentation periodically.

xfs_fsr improves the organization of mounted filesystems. The reorganization algorithm operates on one file at a time, compacting or otherwise improving the layout of the file extents (contiguous blocks of file data).

#### Inspect fragmentation levels

To see how much fragmentation your file system currently has:

    # xfs_db -c frag -r /dev/sda3

#### Perform defragmentation

To begin defragmentation, use the `xfs_fsr` command which is included with the xfsprogs package.

    # xfs_fsr /dev/sda3

## See also

- XFS FAQ
- Improving Metadata Performance By Reducing Journal Overhead
- XFS Wikipedia Entry

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- File systems