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mmrestripefs Command
Assuming that you have enough nodes to saturate the disk servers, and have to move all of the data, the
time to read and write every block of data is roughly:
2 * fileSystemSize / averageDiskserverDataRate
As an upper bound, due to overhead of scanning all of the metadata, this time should be doubled. If other
jobs are heavily loading the virtual shared disk servers, this time may increase even more.
Note: There is no particular reason to stop all other jobs while the mmrestripefs command is running.
The CPU load of the command is minimal on each node and only the files that are being restriped
at any moment are locked to maintain data integrity.
Parameters
Device
The device name of the file system to be restriped. File system names need not be fully-qualified.
fs0 is as acceptable as /dev/fs0.
This must be the first parameter.
-N {Node[,Node...] | NodeFile | NodeClass}
Specify the nodes that participate in the restripe of the file system. This command supports all
defined node classes. The default is all (all nodes in the GPFS cluster will participate in the
restripe of the file system).
Options
For general information on how to specify node names, see “Specifying nodes as input to GPFS
commands” on page 4.
-b Rebalances all files across all disks that are not suspended, even if they are stopped. Although
blocks are allocated on a stopped disk, they are not written to a stopped disk, nor are reads
allowed from a stopped disk, until that disk is started and replicated data is copied onto it. The
mmrestripefs command rebalances and restripes the file system. Use this option to rebalance the
file system after adding, changing, or deleting disks in a file system.
Note: Rebalancing of files is an I/O intensive and time consuming operation, and is important only
for file systems with large files that are mostly invariant. In many cases, normal file update
and creation will rebalance your file system over time, without the cost of the rebalancing.
-m Migrates all critical data off any suspended disk in this file system. Critical data is all data that
would be lost if currently suspended disks were removed.
-P PoolName
Directs mmrestripefs to repair only files assigned to the specified storage pool.
-p Directs mmrestripefs to repair the file placement within the storage pool.
Files assigned to one storage pool, but with data in a different pool, will have their data migrated
to the correct pool. Such files are referred to as ill-placed. Utilities, such as the mmchattr
command, may change a file’s storage pool assignment, but not move the data. The
mmrestripefs command may then be invoked to migrate all of the data at once, rather than
migrating each file individually. Note that the rebalance operation, specified by the -b option, also
performs data placement on all files, whereas the placement option, specified by -p, rebalances
only the files that it moves.
-r Migrates all data off suspended disks. It also restores all replicated files in the file system to their
designated degree of replication when a previous disk failure or removal of a disk has made some
replica data inaccessible. Use this parameter either immediately after a disk failure to protect
replicated data against a subsequent failure, or before taking a disk offline for maintenance to
protect replicated data against failure of another disk during the maintenance process.
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