mmnsddiscover command

Rediscovers paths to the specified network shared disks.

Synopsis

mmnsddiscover [-a | -d "Disk[;Disk...]" | -F DiskFile] [-C ClusterName]
   [-N {Node[,Node...] | NodeFile | NodeClass}]

Availability

Available on all IBM Storage Scale editions.

Description

The mmnsddiscover command is used to rediscover paths for GPFS NSDs on one or more nodes. If you do not specify a node, GPFS rediscovers NSD paths on the node from which you issued the command.

On server nodes, mmnsddiscover causes GPFS to rediscover access to disks, thus restoring paths which may have been broken at an earlier time. On client nodes, mmnsddiscover causes GPFS to refresh its choice of which NSD server to use when an I/O operation occurs.

In general, after the path to a disk is fixed, the mmnsddiscover command must be first run on the server that lost the path to the NSD. After that, run the command on all client nodes that need to access the NSD on that server. You can achieve the same effect with a single mmnsddiscover invocation if you utilize the -N option to specify a node list that contains all the NSD servers and clients that need to rediscover paths.

If you change the NSD server list by using the mmchnsd command, the server list change might not be observed by remote mounts if you are using an IBM Storage Scale release lower than 5.1.6. This is because the change does not get communicated beyond the cluster boundary. Starting with IBM Storage Scale 5.1.6, after you run the mmchnsd commands, run the mmnsddiscover -C <remote cluster name> command on remote mounts and issue I/O to the disk so that server rechoose can take place. This feature is only available when the node that handles the mmchnsd command and the file system manager both are on 5.1.6 code level. This feature does not require the node that has the remote mounts to be on 5.1.6 code level.

Parameters

-a: Rediscovers paths for all NSDs. This is the default.
-d "DiskName[;DiskName]": Specifies a list of NSDs whose paths are to be rediscovered.
-F DiskFile: Specifies a file that contains the names of the NSDs whose paths are to be rediscovered.
-C ClusterName: Specifies the name of the cluster to which the NSDs belong. This defaults to the local cluster if not specified.
-N {Node[,Node...] | NodeFile | NodeClass}: Specifies the nodes on which the rediscovery is to be done.
For general information on how to specify node names, see Specifying nodes as input to GPFS commands.

Exit status

0: Successful completion.
nonzero: A failure has occurred.

Security

You must have root authority to run the mmnsddiscover 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.

Examples

To rediscover the paths for all of the NSDs in the local cluster on the local node, issue the command:
```
 mmnsddiscover
```
The system displays output similar to:
```
mmnsddiscover:  Attempting to rediscover the disks.  
   This may take a while ...

mmnsddiscover:  Finished.
```
To rediscover the paths for all of the NSDs in the local cluster on all nodes in the local cluster, issue the command:
```
mmnsddiscover -a -N all
```
The system displays output similar to:
```
mmnsddiscover:  Attempting to rediscover the disks.  
   This may take a while ...

mmnsddiscover:  Finished.
```

To rediscover the paths for a given list of the NSDs on a node in the local cluster, issue the command:

mmnsddiscover -d "gpfs1nsd;gpfs2nsd" -N c6f2c2vp5

The system displays output similar to:

mmnsddiscover: Attempting to rediscover the disks. This may take a while ...
c6f2c2vp5.ppd.pok.ibm.com: GPFS: 6027-1805 [N] Rediscovered nsd server access to gpfs1nsd.
c6f2c2vp5.ppd.pok.ibm.com: GPFS: 6027-1805 [N] Rediscovered nsd server access to gpfs2nsd.
mmnsddiscover: Finished.

Location

/usr/lpp/mmfs/bin