Enabling and Disabling Input/Output (I/O) Controllers

DMP allows you to turn off I/O to a host I/O controller so that you can perform administrative operations. This feature can be used for maintenance of controllers attached to the host or of disk arrays supported by VxVM. I/O operations to the host I/O controller can be turned back on after the maintenance task is completed. You can accomplish these operations using the vxdmpadm command provided with VxVM.

In Active/Active type disk arrays, VxVM uses a balanced path mechanism to schedule I/O to multipathed disks. As a result, I/O may go through any available path at any given point in time. For example, if a system has an Active/Active storage array and you need to change an interface board that is connected to this disk array (if supported by the hardware), you can use the vxdmpadm command to list the host I/O controllers that are connected to the interface board. Disable the host I/O controllers to stop further I/O to the disks that are accessed through the interface board. You can then replace the board without causing disruption to any ongoing I/O to disks in the disk array.

In Active/Passive type disk arrays, VxVM schedules I/O to use the primary path until a failure is encountered. To change an interface card on the disk array or a card on the host (if supported by the hardware) that is connected to the disk array, disable I/O operations to the host I/O controllers. This shifts all I/O over to an active secondary path or to an active primary path on another I/O controller so that you can change the hardware.

After the operation is over, you can use vxdmpadm to re-enable the paths through the controllers.