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mmdefragfs Command
Name
mmdefragfs – Reduces disk fragmentation by increasing the number of full free blocks available to the file
system.
Synopsis
mmdefragfs Device [-i] [-v] [-u BlkUtilPct]
Description
Use the mmdefragfs command to reduce fragmentation of a file system. The mmdefragfs command
moves existing file system data within a disk to make more efficient use of disk blocks. The data is
migrated to unused subblocks in partially allocated blocks, thereby increasing the number of free full
blocks.
The mmdefragfs command can be run against a mounted or unmounted file system. However, best
results are achieved when the file system is unmounted. When a file system is mounted, allocation status
may change causing retries to find a suitable unused subblock.
If mmdefragfs is issued on a file that is locked by SANergy, the file is not de-fragmented.
Parameters
Device
Options
The device name of the file system to have fragmentation reduced. File system names need not
be fully-qualified. fs0 is as acceptable as /dev/fs0.
This must be the first parameter.
-i Specifies to query the current disk fragmentation state of the file system. Does not perform the
actual defragmentation of the disks in the file system.
-u BlkUtilPct
The average block utilization goal for the disks in the file system. The mmdefragfs command
reduces the number of allocated blocks by increasing the percent utilization of the remaining
blocks. The command automatically goes through multiple iterations until BlkUtilPct is achieved on
all of the disks in the file system or until no progress is made in achieving BlkUtilPct from one
iteration to the next, at which point it exits.
-v Specifies that the output is verbose.
Exit status
0 Successful completion.
nonzero A failure has occurred.
Security
You must have root authority to run the mmdefragfs command.
You may issue the mmdefragfs command from any node in the GPFS cluster.
146 GPFS: Administration and Programming Reference