mmchpool command

Modifies storage pool properties.

Synopsis

mmchpool Device {PoolName[,PoolName...] | all}
         [--block-group-factor BlockGroupFactor]
         [--write-affinity-depth WriteAffinityDepth]

or

mmchpool Device -F PoolDescriptorFile

Availability

Available on all IBM Spectrum Scale editions.

When running the mmchpool command, the file system must be unmounted on all nodes.

Description

Use the mmchpool command to change storage pool properties.

Parameters

Device
Specifies the device name of the file system for which storage pool information is to be changed. File system names do not need to be fully qualified; for example, fs0 is as acceptable as /dev/fs0.
PoolName[,PoolName...]
Specifies one or more storage pools for which attributes will be changed.
all
Changes the attributes for all the storage pools in the specified file system.
--block-group-factor BlockGroupFactor
Specifies how many file system blocks are laid out sequentially on disk to behave like a single large block. This option only works if --allow-write-affinity is set for the data pool. This applies only to a new data block layout; it does not migrate previously existing data blocks.
--write-affinity-depth WriteAffinityDepth
Specifies the allocation policy to be used. This option only works if --allow-write-affinity is set for the data pool. This applies only to a new data block layout; it does not migrate previously existing data blocks.
-F PoolDescriptorFile
Specifies a file used to describe the storage pool attributes. The file contains one line per storage pool, in the following format:
%pool:name:blockSize:diskUsage:reserved:maxDiskSize:allocationType:allowWriteAffinity:writeAffinityDepth:blockGroupFactor:

Exit status

0
Successful completion.
nonzero
A failure has occurred.

Security

You must have root authority to run the mmchpool command.

The node on which the command is issued must be able to execute remote shell commands on any other node in the cluster without the use of a password and without producing any extraneous messages. For more information, see Requirements for administering a GPFS file system.

Example

For example, to change the writeAffinityDepth to 2 for FPO pool pool1 of file system fs1, issue this command: 
mmchpool fs1 pool1 --write-affinity-depth 2
To confirm the change, issue this command: 
mmlspool fs1 pool1 -L
The system displays information similar to the following: 
# mmlspool fs_1 p1 -L
Pool:
  name                   = pool1
  poolID                 = 65537
  blockSize              = 4 MB
  usage                  = dataOnly
  maxDiskSize            = 11 TB
  layoutMap              = cluster
  allowWriteAffinity     = yes
  writeAffinityDepth     = 2
  blockGroupFactor       = 128

See also

Location

/usr/lpp/mmfs/bin