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136 Administering dynamic multipathing (DMP)
Enabling and disabling I/O for controllers and storage processors
Enabling and disabling I/O for controllers and
storage processors
DMP allows you to turn off I/O for a controller or the array port of a storage
processor so that you can perform administrative operations. This feature can
be used for maintenance of HBA controllers on the host, or array ports that are
attached to disk arrays supported by VxVM. I/O operations to the controller or
array port 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 controllers that are connected to the interface board.
Disable the 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 the interface card for an array port or
an HBA controller card on the host (if supported by the hardware) that is
connected to the disk array, disable I/O operations to the array port or to the
HBA controller. This shifts all I/O over to an active secondary path or to an
active primary path on another 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.
See “Disabling I/O for paths, controllers or array ports” on page 153.
See “Enabling I/O for paths, controllers or array ports” on page 154.
See “Upgrading disk controller firmware” on page 154.
Note: From release 5.0 of VxVM, these operations are supported for controllers
that are used to access disk arrays on which cluster-shareable disk groups are
configured.