GPFS: Administration and Programming Reference - IRA Home

mmrestripefs Command
Name
mmrestripefs - Rebalances or restores the replication factor of all files in a file system.
Synopsis
mmrestripefs Device {-m | -r | -b | -p} [-N {Node[,Node...] | NodeFile | NodeClass}] [-P PoolName]
Description
Use the mmrestripefs command to rebalance or restore the replication factor of all files in a file system.
The mmrestripefs command moves existing file system data between different disks in the file system
based on changes to the disk state made by the mmchdisk, mmadddisk, and mmdeldisk commands.
The mmrestripefs command attempts to restore the metadata or data replication factor of any file in the
file system.
You must specify one of the four options (-b, -m, -r, or -p) to indicate how much file system data to move.
You can issue this command against a mounted or unmounted file system.
If you do not use replication, the -m and -r options are equivalent. Their behavior differs only on replicated
files. After a successful replicate (-r option), all suspended disks are empty. A migrate operation, using the
-m option, leaves data on a suspended disk as long as at least one other replica of the data remains on a
disk that is not suspended. Restriping a file system includes replicating it. The -b option performs all the
operations of the -m and -r options.
Consider the necessity of restriping and the current demands on the system. New data that is added to
the file system is correctly striped. Restriping a large file system requires a large number of insert and
delete operations and may affect system performance. Plan to perform this task when system demand is
low.
When using SANergy, consider these points:
v If the mmrestripefs command is issued on a file that is locked by SANergy, the command waits until it
is unlocked before proceeding.
v I/O operations from SANergy clients must terminate before using the mmrestripefs command. If not,
the client applications receive an error.
Determining how long mmrestripefs takes to complete
To determine how long the mmrestripefs command will take to complete, consider these points:
1. How much data is to be moved by issuing the df -k command.
2. How many GPFS client nodes there are to do the work.
3. How much virtual shared disk server or Network Shared Disk (NSD) server bandwidth is available for
I/O.
4. If you have added new disks to a file system, after the disks have been added determine how much
free space is on each of the new disks by issuing the mmdf Device - q command.
The restriping of a file system is done by having one thread on each node in the cluster work on a subset
of files. Consequently, the more GPFS client nodes performing work for the restripe, the faster the
mmrestripefs command will complete. The nodes that should participate in the restripe are specified on
the command using the -N parameter. Based on raw I/O rates, you should be able to estimate the length
of time for the restripe. However, to account for the overhead of scanning all metadata, that value should
be doubled.
Chapter 8. GPFS commands 255