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xfs_fsr(8) System Manager's Manual xfs_fsr(8)
NAME
xfs_fsr - filesystem reorganizer for XFS
SYNOPSIS
xfs_fsr [-vdg] [-t seconds] [-p passes] [-f leftoff] [-m mtab]
xfs_fsr [-vdg] [xfsdev | file] ...
xfs_fsr -V
DESCRIPTION
xfs_fsr is applicable only to XFS filesystems.
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).
The following options are accepted by xfs_fsr. The -m, -t, and -f options have no meaning
if any filesystems or files are specified on the command line.
-m mtab Use this file for the list of filesystems to reorganize. The default is to
use /etc/mtab.
-t seconds How long to reorganize. The default is 7200 seconds (2 hours).
-p passes Number of passes before terminating global re-org. The default is 10 passes.
-f leftoff Use this file instead of /var/tmp/.fsrlast to read the state of where to
start and as the file to store the state of where reorganization left off.
-v Verbose. Print cryptic information about each file being reorganized.
-d Debug. Print even more cryptic information.
-g Print to syslog (default if stdout not a tty).
-V Prints the version number and exits.
When invoked with no arguments xfs_fsr reorganizes all regular files in all mounted
filesystems. xfs_fsr makes many cycles over /etc/mtab each time making a single pass over
each XFS filesystem. Each pass goes through and selects files that have the largest num-
ber of extents. It attempts to defragment the top 10% of these files on each pass.
It runs for up to two hours after which it records the filesystem where it left off, so it
can start there the next time. This information is stored in the file /var/tmp/.fsr-
last_xfs. If the information found here is somehow inconsistent or out of date it is
ignored and reorganization starts at the beginning of the first filesystem found in
/etc/mtab.
xfs_fsr can be called with one or more arguments naming filesystems (block device name),
and files to reorganize. In this mode xfs_fsr does not read or write /var/tmp/.fsr-
last_xfs nor does it run for a fixed time interval. It makes one pass through each speci-
fied regular file and all regular files in each specified filesystem. A command line name
referring to a symbolic link (except to a file system device), FIFO, or UNIX domain socket
generates a warning message, but is otherwise ignored. While traversing the filesystem
these types of files are silently skipped.
FILES
/etc/mtab contains default list of filesystems to reorganize.
/var/tmp/.fsrlast_xfs
records the state where reorganization left off.
SEE ALSO
xfs_fsr(8), mkfs.xfs(8), xfs_ncheck(8), xfs(5).
NOTES
xfs_fsr improves the layout of extents for each file by copying the entire file to a tem-
porary location and then interchanging the data extents of the target and temporary files
in an atomic manner. This method requires that enough free disk space be available to
copy any given file and that the space be less fragmented than the original file. It also
requires the owner of the file to have enough remaining filespace quota to do the copy on
systems running quotas. xfs_fsr generates a warning message if space is not sufficient to
improve the target file.
A temporary file used in improving a file given on the command line is created in the same
parent directory of the target file and is prefixed by the string '.fsr'. The temporary
files used in improving an entire XFS device are stored in a directory at the root of the
target device and use the same naming scheme. The temporary files are unlinked upon cre-
ation so data will not be readable by any other process.
xfs_fsr does not operate on files that are currently mapped in memory. A 'file busy'
error can be seen for these files if the verbose flag (-v) is set.
Files marked as no-defrag will be skipped. The xfs_io(8) chattr command with the f
attribute can be used to set or clear this flag. Files and directories created in a direc-
tory with the no-defrag flag will inherit the attribute.
An entry in /etc/mtab or the file specified using the -m option must have the rw option
specified for read and write access. If this option is not present, then xfs_fsr skips
the filesystem described by that line. See the fstab(5) reference page for more details.
In general we do not foresee the need to run xfs_fsr on system partitions such as /, /boot
and /usr as in general these will not suffer from fragmentation. There are also issues
with defragmenting files lilo(8) uses to boot your system. It is recommended that these
files should be flagged as no-defrag with the xfs_io(8) chattr command. Should these files
be moved by xfs_fsr then you must rerun lilo before you reboot or you may have an
unbootable system.
xfs_fsr(8)
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