IBM General Parallel File System for AIX: Administration and Programming Reference
Name
mmchdisk - Changes state or parameters of one or more disks
in a GPFS file system.
Synopsis
mmchdisk Device {suspend | resume |
stop | start | change} -d
"DiskDesc[;DiskDesc...
]" [-N { all | mount |
NodeName[,NodeName ... ] }
]
Or,
mmchdisk Device { resume | start }
-a [-N { all | mount |
NodeName[,NodeName ... ] }
]
Description
Use the mmchdisk command to change the state or the parameters of
one or more disks in a GPFS file system.
The state of a disk is a combination of its status and availability,
displayable with the mmlsdisk command.
Disk status is either ready or suspended.
Transitional status of replacing, replacement, or being
emptied might also appear if a disk is being deleted or replaced.
A suspended disk is one that the user has decided not to place any new data
on. Existing data on a suspended disk may still be read or
updated. Typically, a disk is suspended prior to restriping a file
system. Suspending a disk tells the mmrestripefs command that data should be migrated
off that disk. Data may be read from a suspended disk. Disk
availability is either up or down.
Be sure to use stop before you take a disk off-line for
maintenance. You should also use stop when a disk has become
temporarily inaccessible due to a disk failure that is repairable without loss
of data on that disk (for example, an adapter failure or a failure of the disk
electronics).
The Disk Usage (dataOnly, metadataOnly, or
dataAndMetadata) and Failure Group parameters of a disk are
adjusted with the change option (see the IBM
General Parallel File System for AIX: Concepts, Planning, and
Installation Guide and search for recoverability
considerations). mmchdisk change does not move data or
metadata that resides on the disk. After changing disk parameters, in
particular, Disk Usage, you may have to issue the
mmrestripefs command with the -r option to relocate data so
that it conforms to the new disk parameters.
The mmchdisk command can be issued for a mounted or unmounted file
system. When maintenance is complete or the failure has been repaired,
use the mmchdisk command with the start option. If
the failure cannot be repaired without loss of data, you can use the
mmdeldisk command.
Parameters
- Device
- The device name of the file system to which the disks belong. File
system names need not be fully qualified. fs0 is as acceptable
as /dev/fs0.
This must be the first parameter.
- -d "DiskDesc[;DiskDesc...
]"
- A descriptor for each disk to be changed. In an SP environment, you must use the virtual shared disk
name. In an HACMP environment, you must use the logical volume
name.
Specify only disk names when using the suspend, resume,
stop, or start options. Delimit multiple disk names
with semicolons and enclose list in quotation marks. For example,
"gpfs1vsd;gpfs2vsd"
When using the change option, include the disk name and any new
Disk Usage and Failure Group positional parameter values in
the descriptor. Delimit descriptors with semicolons and enclose list in
quotation marks, for example,
"gpfs1vsd:::dataOnly;gpfs2vsd:::metadataOnly:12"
Disk descriptors
Each disk descriptor must be specified in the form:
DiskName:::DiskUsage:FailureGroup
- DiskName
- In an SP environment, you must specify the virtual shared disk
name. For details on generating a virtual shared disk, see Specifying disk descriptors and the mmcrvsd
command. To use an existing virtual shared disk in the file system,
only the virtual shared disk name need be specified in the disk
descriptor. GPFS performance and recovery processes function best with
one disk per virtual shared disk. If you want to create virtual shared
disks with more than one disk, refer to the IBM Parallel System Support Programs for
AIX: Managing Shared Disks manual.
In an HACMP environment, you must specify the logical volume name.
For details on generating a logical volume, see Specifying disk descriptors and the mmcrlv command.
To use an existing logical volume group in the file system, only the logical
volume name need be specified in the disk descriptor. The disk name
must be set up the same on all of the nodes in the nodeset.
Logical volume use in an HACMP environment:
- Any disk resources (volume groups and logical volumes) that will be used
by GPFS must not belong to any HACMP/ES resource group. HACMP/ES will
not be in control of these disk resources and is not responsible for varying
them on or off at any time. The responsibility to keep the disks in the
proper state belongs to GPFS in the HACMP environment. For further
information on logical volume concepts, see the AIX System Management Guide:
Operating System and Devices.
- When using single-node quorum Fibre Channel attached disks are not
supported.
- Disk Usage
- If a value is not specified, the disk usage remains unchanged:
- dataAndMetadata
- dataOnly
- metadataOnly
- Failure Group
- A number identifying the failure group to which this disk belongs.
You can specify any value from -1 (where -1 indicates that the disk has no
point of failure in common with any other disk) to 4000. If you do not
specify a failure group, the value remains unchanged.
- -a
- Specifies to change the state of all of the disks belonging to the file
system, Device. This operand is only valid on the
resume and start options.
- -N {all | mount |
NodeName[,NodeName ... ] }
- Specify the nodes to participate in the restripe of the file system after
the state or parameters of the disks have been changed. Valid values
are:
- all
- Indicates that all nodes in the GPFS nodeset, whether or not they have the
file system mounted, should participate in the restripe. This is the
default when the -N option has not been specified.
- mount
- Indicates that only the nodes which have the file system mounted should
participate in the restripe of the file system.
- NodeName[,NodeName ... ]
- A comma-separated list of target nodes that should participate in the
restripe.
The hostname or IP address used for a node must refer to the adapter port
over which the GPFS daemons communicate. Alias interfaces are not
allowed. Use the original address or a name that is resolved by the
host command to that original address. You may specify a node
using any of these forms:
| Format
| Example
|
| Short hostname
| k145n01
|
| Long hostname
| k145n01.kgn.ibm.com
|
| IP address
| 9.119.19.102
|
Options
- suspend
- Instructs GPFS to stop allocating space on the specified disk.
Place a disk in this state when you are preparing to restripe the file system
off this disk because of faulty performance. This is a user-initiated
state that GPFS never uses without an explicit command to change disk
state.
- Note:
- A disk remains suspended until it is explicitly resumed. Restarting
GPFS or rebooting nodes does not restore normal access to a suspended
disk.
- resume
- Informs GPFS that a disk previously suspended is now available for
allocating new space. If the disk is currently in a stopped state, it
remains stopped until you specify the start option. Otherwise,
normal read and write access to the disk resumes.
- stop
- Instructs GPFS to stop any attempts to access the specified disks.
Use this option to tell the File System Manager that a disk has failed or is
currently inaccessible because of maintenance.
- Note:
- A disk remains stopped until it is explicitly started by the
mmchdisk command with the start option. Restarting
the GPFS Server daemon or rebooting does not restore normal access to a
stopped disk.
- start
- Informs GPFS that disks previously stopped are now accessible. This
is accomplished by first changing the disk availability from down to
recovering. The file system metadata is then scanned and any
missing updates (replicated data that was changed while the disk was down) are
repaired. If this operation is successful, the availability is then
changed to up. If the metadata scan fails, availability is set
to unrecovered. This could occur if too many other disks are
down. The metadata scan can be reinitiated at a later time by issuing
the mmchdisk start command again.
- Note:
- If more than one disk in the file system is down, they should all be started
at the same time by issuing the mmchdisk Device start -a
command. If you start them separately and metadata is stored on any
disk that remains down, the mmchdisk start command fails.
- change
- Instructs GPFS to change the Disk Usage parameter, the
Failure Group parameter, or both, according to the values specified
in the DiskDesc.
Exit status
- 0
- Successful completion.
- 1
- A failure has occurred.
Security
You must have root authority to run the mmchdisk command.
In an SP environment:
- Verify the authentication method set for SP security services:
- If your authentication method is set to compatibility, Kerberos
authentication is required. Issue the k4init command.
- If your authentication method is set to DCE, dce_login
authentication is required.
- 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.
- You may issue the mmchdisk command from any node running GPFS or
the CWS.
- If you are executing mmchdisk 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:
- 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:
- Proper authorization is granted to all nodes in the GPFS cluster.
- The nodes in the GPFS cluster can communicate without the use of a
password.
- You may issue the mmchdisk command from any node in the GPFS
cluster.
Examples
- To suspend active disk gpfs1vsd , enter:
mmchdisk fs0 suspend -d gpfs1vsd
To confirm the change, enter:
mmlsdisk fs0
The system displays information similar to:
disk driver sector failure holds holds
name type size group metadata data status availability
------------ -------- ------ ------- -------- ----- ------------- ------------
gpfs1vsd disk 512 -1 yes yes suspended up
gpfs2vsd disk 512 -1 yes yes ready up
gpfs3vsd disk 512 -1 yes yes ready up
gpfs4vsd disk 512 -1 yes yes ready up
- To specify that metadata should no longer be stored on disk gpfs1vsd ,
enter:
mmchdisk fs0 change -d "gpfs1vsd:::dataOnly"
To confirm the change, enter:
mmlsdisk fs0
The system displays information similar to:
disk driver sector failure holds holds
name type size group metadata data status availability
------------ -------- ------ ------- -------- ----- ------------- ------------
gpfs1vsd disk 512 -1 no yes ready up
gpfs2vsd disk 512 -1 yes yes ready up
gpfs3vsd disk 512 -1 yes yes ready up
gpfs4vsd disk 512 -1 yes yes ready up
See also
Displaying GPFS disk states
mmadddisk Command
mmdeldisk Command
mmlsdisk Command
mmrpldisk Command
Location
/usr/lpp/mmfs/bin
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