detectmdisk

The detectmdisk command allows you to manually rescan the fibre-channel network for any new managed disks (MDisks) that might have been added and to rebalance MDisk access across all available controller device ports.

Syntax


>>- svctask -- -- detectmdisk ---------------------------------><

Description

This command causes the cluster to rescan the fibre-channel network. The rescan discovers any new MDisks that have been added to the cluster and rebalances MDisk access across the available controller device ports. This command also detects any loss of controller port availability, and updates the SAN Volume Controller configuration to reflect any changes.

Note: Although it might appear that the detectmdisk command has completed, some extra time might be required for it to run. The detectmdisk is asynchronous and returns a prompt while the command continues to run in the background. You can use the lsdiscoverystatus command to list the discovery status.

In general, the cluster automatically detects disks when they appear on the network. However, some fibre-channel controllers do not send the required SCSI primitives that are necessary to automatically discover the new disks.

If you have attached new storage and the cluster has not detected it, you might need to run this command before the cluster detects the new disks.

When back-end controllers are added to the fibre-channel SAN and are included in the same switch zone as a cluster, the cluster automatically discovers the back-end controller and determines what storage is presented to it. The SCSI LUs that are presented by the back-end controller are displayed as unmanaged MDisks. However, if the configuration of the back-end controller is modified after this has occurred, the cluster might be unaware of these configuration changes. Run this command to rescan the fibre-channel network and update the list of unmanaged MDisks.

Note: The automatic discovery that is performed by the cluster does not write to an unmanaged MDisk. Only when you add an MDisk to an MDisk group, or use an MDisk to create an image mode virtual disk, is the storage actually used.

To identify the available MDisks, issue the svctask detectmdisk command to scan the fibre-channel network for any MDisks. When the detection is complete, issue the svcinfo lsmdiskcandidate command to show the unmanaged MDisks; these MDisks have not been assigned to an MDisk group. Alternatively, you can issue the svcinfo lsmdisk command to view all of the MDisks.

If disk controller ports have been removed as part of a reconfiguration, the SAN Volume Controller detects this change and reports the following error because it cannot distinguish an intentional reconfiguration from a port failure:

1630 Number of device logins reduced

If the error persists and redundancy has been compromised, the following more serious error is reported:

1627 Insufficient redundancy in disk controller connectivity

You must issue the svctask detectmdisk command to force SAN Volume Controller to update its configuration and accept the changes to the controller ports.

Note: Only issue the svctask detectmdisk command when all of the disk controller ports are working and correctly configured in the controller and the SAN zoning. Failure to do this could result in errors not being reported.

An invocation example

svctask detectmdisk

The resulting output

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