Veritas Dynamic Multipathing (VxDMP) Command Line Reference (Cheat Sheet)

The vxdmpadm utility is a command line administrative interface to the DMP feature of VxVM. You can use the vxdmpadm utility to perform the following tasks:

  • Retrieve the name of the DMP device corresponding to a particular path
  • List all paths under a DMP device
  • List all controllers connected to disks attached to the host
  • List all the paths connected to a particular controller
  • Enable or disable a host controller on the system
  • Rename an enclosure
  • Control the operation of the DMP restore daemon

The following sections cover these tasks in detail along with sample output. For more information, see the vxdmpadm manual page.

Retrieving Information About a DMP Node

1. The following command displays the DMP node that controls a particular physical path:

# vxdmpadm getdmpnode nodename=c3t2d1

The physical path can be specified as the nodename attribute, which must be a valid path listed in the /dev/rdsk directory.

2. Use the enclosure attribute with getdmpnode to obtain a list of all DMP nodes for the specified enclosure.

# vxdmpadm getdmpnode enclosure=enc0

3. Displaying All Paths Controlled by a DMP Node. The following command displays the paths controlled by the specified DMP node:

# vxdmpadm getsubpaths dmpnodename=c2t1d0s2

The specified DMP node must be a valid node in the /dev/vx/rdmp directory.

You can also use getsubpaths to obtain all paths through a particular host disk controller:

# vxdmpadm getsubpaths ctlr=c2

Listing Information About Host I/O Controllers

1. The following command lists attributes of all host I/O controllers on the system:

# vxdmpadm listctlr all

2. This form of the command lists controllers belonging to a specified enclosure and enclosure type:

# vxdmpadm listctlr enclosure=enc0 type=X1

Disabling a Controller

Disabling I/O to a host disk controller prevents DMP from issuing I/O through the specified controller. The command blocks until all pending I/O issued through the specified disk controller are completed.

To disable a controller, use the following command:

# vxdmpadm disable ctlr=ctlr

Enabling a Controller

Enabling a controller allows a previously disabled host disk controller to accept I/O. This operation succeeds only if the controller is accessible to the host and I/O can be performed on it. When connecting active/passive disk arrays in a non-clustered environment, the enable operation results in failback of I/O to the primary path. The enable operation can also be used to allow I/O to the controllers on a system board that was previously detached.

To enable a controller, use the following command:

# vxdmpadm enable ctlr=ctlr

Listing Information About Enclosures

1. To display the attributes of a specified enclosure, use the following command:

# vxdmpadm listenclosure enc0

2. The following command lists attributes for all enclosures in a system:

# vxdmpadm listenclosure all

Renaming an Enclosure

The vxdmpadm setattr command can be used to assign a meaningful name to an existing enclosure, for example:

# vxdmpadm setattr enclosure enc0 name=GRP_1

This example changes the name of the enclosure from enc0 to GRP_1.

Starting the DMP Restore Daemon

The DMP restore daemon re-examines the condition of paths at a specified interval. The type of analysis it performs on the paths depends on the specified checking policy. Use the start restore command to start the restore daemon and specify the policy:

# vxdmpadm start restore policy=check_disabled

The check_disabled policy (the default) checks the condition of paths that were previously disabled due to hardware failures and revives them if they are back online. If the policy is set to check_all, the restore daemon analyzes all paths in the system and revives the paths that are back online, as well as disabling the paths that are inaccessible.

The command vxdmpadm start restore is used to set the interval of polling. For example, the polling interval is set to 400 seconds using the following command:

# vxdmpadm start restore interval=400

The default interval is 300 seconds. Decreasing this interval can adversely affect system performance. To change the interval or policy, you must stop the restore daemon and restart it with new attributes.

Stopping the DMP Restore Daemon

Use the following command to stop the DMP restore daemon:

# vxdmpadm stop restore

Displaying the Status of the DMP Restore Daemon

Use the following command to display the status of the automatic path restoration daemon, its polling interval, and the policy that it uses to check the condition of paths:

# vxdmpadm stat restored

This produces output such as the following:

The number of daemons running : 1
The interval of daemon: 300
The policy of daemon: check_disabled

Displaying Information About the DMP Error Daemons

To display the number of error daemons that are running, use the following command:

# vxdmpadm stat errord