xfs_fsr

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 ex
   tents (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 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/.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  If the information found here is somehow inconsistent or out of date it is ignored and reorganization starts at the beginning of the first filesystem found in /etc/mtab.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/.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 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 temporary 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 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 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.

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