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 reorgani-
zation 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 op-
tions 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 de-
fault 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 number 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/.fsrlast_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is somehow inconsistent or out of date it is ignored and reorganization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/.fsrlast_xfs nor does it run for a fixed time
interval. It makes one pass through each specified regular file and all
regular files in each specified filesystem. A command line name refer-
ring 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 en-
tire file to a temporary location and then interchanging the data ex-
tents 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 file-
space 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
creation 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 directory 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 parti-
tions 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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