detectmdisk

Use the detectmdisk command to manually rescan the Internet Small Computer Systems Interface (iSCSI) or Fibre Channel (FC) network for any new managed disks (MDisks) that might have been added, and to rebalance MDisk access across all available controller device ports.

Syntax

detectmdisk -scope scope_id

Parameters

-scopescope_id: (Optional) Specifies the domain index. The value must be a number from 0 to 6 For example, the value 0 indicates FC and 6 indicates iSCSI.

Description

This command causes the clusterd system (system) to rescan the FC or iSCSI network. The rescan discovers any new MDisks that have been added to the system and rebalances MDisk access across the available controller device ports. This command also detects any loss of controller port availability, and updates the Storwize V5000 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 system automatically detects disks when they appear on the network. However, some FC 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 system has not detected it, you might need to run this command before the system detects the new disks.

When back-end controllers are added to the FC SAN and are included in the same switch zone as a system, the system 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 system might be unaware of these configuration changes. Run this command to rescan the FC or iSCSI network and update the list of unmanaged MDisks.

Note: The automatic discovery that is performed by the system does not write to an unmanaged MDisk. Only when you add an MDisk to a storage pool, or use an MDisk to create an image mode volume, is the storage actually used.

To identify the available MDisks, issue the detectmdisk command to scan the FC or iSCSI network for any MDisks. When the detection is complete, issue the lsmdiskcandidate command to show the unmanaged MDisks; these MDisks have not been assigned to a storage pool. Alternatively, you can issue the lsmdisk command to view all of the MDisks.

If disk controller ports have been removed as part of a reconfiguration, the Storwize V5000 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 detectmdisk command to force the Storwize V5000 to update its configuration and accept the changes to the controller ports.

Note: Only issue the 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

detectmdisk

The resulting output:

No feedback

An invocation example

detectmdisk -scope 1

The resulting output:

No feedback