Administering DMP Using vxdmpadm

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(1M) manual page.

Retrieving Information About a DMP Node

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

# vxdmpadm getdmpnode nodename=c3t2d1

/dev/rdsk directory.

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

# vxdmpadm getdmpnode enclosure=enc0

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

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

# vxdmpadm listctlr all

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

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

# vxdmpadm listenclosure enc0

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=GRP1

This example changes the name of an enclosure from enc0 to GRP1.




	NOTE: The maximum length of the enclosure name prefix is 25 characters. The name must not contain an underbar character (_).

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.




	NOTE: The DMP restore daemon does not change the disabled state of the path through a controller that you have disabled using vxdmpadm disable.

Use the start restore command to start the restore daemon and specify one of the following policies:

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 to start the restore daemon with this policy is:
# vxdmpadm start restore policy=check_all [interval=seconds]
check_alternate
The restore daemon checks that at least one alternate path is healthy. It generates a notification if this condition is not met. This policy avoids inquiry commands on all healthy paths, and is less costly than check_all in cases where a large number of paths are available. This policy is the same as check_all if there are only two paths per DMP node. The command to start the restore daemon with this policy is:
# vxdmpadm start restore policy=check_alternate [interval=seconds]
check_disabled
This is the default policy. The restore daemon checks the condition of paths that were previously disabled due to hardware failures, and revives them if they are back online. The command to start the restore daemon with this policy is:
# vxdmpadm start restore policy=check_disabled [interval=seconds]
check_periodic
The restore daemon performs check_all once in a given number of cycles, and check_disabled in the remainder of the cycles. This policy may lead to periodic slowing down (due to check_all) if there are a large number of paths available. The command to start the restore daemon with this policy is:
# vxdmpadm start restore policy=check_periodic interval=seconds [period=number]
The interval attribute must be specified for this policy. The default number of cycles between running the check_all policy is 10.

The interval attribute specifies how often the restore daemon examines the paths. For example, after stopping the restore daemon, the polling interval can be 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.




	NOTE: To change the interval or policy, you must first stop the restore daemon, and then restart it with new attributes.

See the vxdmpadm(1M) manual page for more information about DMP restore policies.

Stopping the DMP Restore Daemon

Use the following command to stop the DMP restore daemon:

# vxdmpadm stop restore




	NOTE: Automatic path failback stops if the restore daemon is stopped.

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