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IBM General Parallel File System for AIX: Administration and Programming Reference

mmchfs Command

Name

mmchfs - Changes the attributes of a GPFS file system.

Synopsis

mmchfs Device [-A {yes | no}] [-F MaxNumInodes] [-m DefaultMetadataReplicas] [-Q {yes | no} ] [-r DefaultDataReplicas] [-T mountpoint] [-V] [-z {yes | no} ]

Or,

mmchfs Device [-C NodesetId]

Description

This command need only be issued on one node in the GPFS nodeset. The changes are propagated through all nodes in the nodeset.

Results

Upon successful completion of the mmchfs command, these tasks are performed:

Parameters

Device
The device name of the file system to be changed.

File system names need not be fully qualified. fs0 is as acceptable as /dev/fs0. However, file system names must be unique across GPFS nodesets.

This must be the first parameter.

-C NodesetId
Move the file system to the indicated nodeset.

The file system must be unmounted on all nodes prior to issuing the command.

Options

-A {yes | no}
Changes whether or not the file system is automatically mounted when the GPFS daemons start.

-F MaxNumInodes
Changes the maximum number of files that can be created. Allowable values range from the current number of created inodes (determined by issuing the mmdf command), through the maximum number of files possibly supported as constrained by the formula:

maximum number of files = (total file system space/2) / (inode size + subblock size)

-m DefaultMetaDataReplicas
Changes the default number of metadata replicas. Valid values are 1 and 2 but cannot exceed the values of MaxMetaDataReplicas set when the file system was created.

-Q {yes | no}
If yes is specified, quotas are activated automatically when the file system is mounted. If no is specified, the quota files remain in the file system, but are not to be used.

To install quotas after the mmchfs command has been issued:

  1. Remount the file system.
  2. Compile inode and disk block statistics using the mmcheckquota command (see Checking quotas). These values should be used as reference to establish realistic quota values when issuing the mmedquota command.
  3. Issue the mmedquota command to set quota values (see Establishing and changing quotas).
  4. Issue the mmquotaon command to activate quota enforcement (see Activating quota enforcement).

-r DefaultDataReplicas
Changes the default number of data replicas. Valid values are 1 and 2 but cannot exceed the values of MaxDataReplicas set when the file system was created.

-T
Change the mountpoint of the file system starting at the next mount of the file system.

The file system must be unmounted on all nodes prior to issuing the command.

-V
Change the file system format to the latest format supported by the currently installed level of GPFS. This will cause the file system to become permanently incompatible with prior releases of GPFS.

-z {yes | no}
Enable or disable DMAPI on the file system. For further information on DMAPI for GPFS, see the IBM General Parallel File System for AIX: Data Management API Guide.

Exit status

0
Successful completion.

1
A failure has occurred.

Security

You must have root authority to run the mmchfs command.

In an SP environment:

  1. Verify the authentication method set for SP security services:
    1. If your authentication method is set to compatibility, Kerberos authentication is required. Issue the k4init command.
    2. If your authentication method is set to DCE, dce_login authentication is required.
    3. If your authentication method is set to NONE/std, there must be an entry in the /etc/sysctl.mmcmd.acl file on every node in the nodeset for the root user at every other node in the nodeset.

    For further information, see the latest IBM Parallel System Support Programs for AIX: Administration Guide, IBM Parallel System Support Programs for AIX: Command and Technical Reference, and RS/6000: Planning Volume 2, Control Workstation and Software Environment manuals at www.rs6000.ibm.com/resource/aix_resource/sp_books/pssp. Search for information on sysctl.

  2. You may issue the mmchfs command from any node running GPFS or the CWS.
  3. If you are executing the mmchfs command from the CWS on a multi-partitioned system, the SP_NAME environment variable must be properly set. It is suggested that you use a separate window for each partition and set the environment variable accordingly. For further information, see the IBM Parallel System Support Programs for AIX: Administration Guide and search for understanding system partitioning.

In an HACMP environment:

  1. When using rcp and rsh for remote communication, a properly configured /.rhosts file must exist in the root user's home directory on each node in the GPFS cluster. If you have designated the use of a different remote communication program on either the mmcrcluster or the mmchcluster command, you must insure:
    1. Proper authorization is granted to all nodes in the GPFS cluster.
    2. The nodes in the GPFS cluster can communicate without the use of a password.
  2. You may issue the mmchfs command from any node in the GPFS cluster.

Examples

To change the default replicas for metadata to 2 and the default replicas for data to 2 for new files created in the fs0 file system, enter: 

mmchfs fs0 -m 2 -r 2

To confirm the change, enter: 

mmlsfs fs0 -m -r

The system displays information similar to: 

flag value          description
---- -------------- -----------------------------------------------------
 -m  2              Default number of metadata replicas
 -r  2              Default number of data replicas

See also

Prior to issuing the -V option, see the IBM General Parallel File System for AIX: Concepts, Planning, and Installation Guide and search for migrating to the latest level of GPFS.

mmcrfs Command

mmdelfs Command

mmdf Command

mmfsck Command

mmlsfs Command

IBM General Parallel File System for AIX: Data Management API Guide

Location

/usr/lpp/mmfs/bin

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