GPFS: Administration and Programming Reference - IRA Home

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GPFS provides the mmcrvsd helper command to ease configuration of /dev disk devices.
In an AIX environment, this command can be used to configure virtual shared disks and
make them accessible to nodes connected over a high performance switch. The output
disk descriptor file from an mmcrvsd command can be used as input to the mmcrnsd
command, since the virtual shared disk names enumerated in that file will appear as /dev
block devices on switch attached nodes.
PrimaryServer
The name of the primary NSD server node.
If this field is omitted, the disk is assumed to be SAN-attached to all nodes in the cluster. If
not all nodes in the cluster have access to the disk, or if the file system to which the disk
belongs is to be accessed by other GPFS clusters, PrimaryServer must be specified.
BackupServer
The name of the backup NSD server node.
If the PrimaryServer has been specified and this field is omitted, it is assumed you do not
want failover in the event that the PrimaryServer fails. If BackupServer is specified and the
PrimaryServer has not been specified, the command fails.
For general information on how to specify node names, see “Specifying nodes as input to
GPFS commands” on page 4.
DiskUsage
Specify a disk usage or accept the default. This field is ignored by the mmcrnsd
command, and is passed unchanged to the output descriptor file produced by the
mmcrnsd command. Possible values are:
dataAndMetadata
Indicates that the disk contains both data and metadata. This is the default.
dataOnly
Indicates that the disk contains data and does not contain metadata.
metadataOnly
Indicates that the disk contains metadata and does not contain data.
mmcrnsd Command
descOnly
Indicates that the disk contains no data and no file metadata. Such a disk is used
solely to keep a copy of the file system descriptor, and can be used as a third
failure group in certain disaster recovery configurations. For more information, see
General Parallel File System: Advanced Administration and search on
Synchronous mirroring utilizing GPFS replication.
FailureGroup
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 defaults to the NSD
primary server node number plus 4000. If an NSD server node is not specified, the value
defaults to -1.
GPFS uses this information during data and metadata placement to assure that no two
replicas of the same block are written in such a way as to become unavailable due to a
single failure. All disks that are attached to the same NSD server or adapter should be
placed in the same failure group.
DesiredName
Specify the name you desire for the NSD to be created. This name must not already be
used as another GPFS disk name, and it must not begin with the reserved string ’gpfs’.
Chapter 8. GPFS commands 127