5-4 Sun StorEdge 3000 Family Installation, Operation, and Service Manual • May 2004
5.1.3 Single-Controller Considerations
In a single-controller configuration, it is important to review the following
guidelines:
■ In a single-controller configuration, keep the controller as the primary controller
at all times and assign all logical drives to the primary controller. The primary
controller controls all logical drive and firmware operations. In a single-controller
configuration, the controller must be the primary controller or the controller
cannot operate.
The secondary controller is used only in dual-controller configurations for
redistributed I/O and for failover.
■ Do not disable the Redundant Controller setting and do not set the
controller as a secondary controller.
Caution – If you disable the Redundant Controller setting and reconfigure the
controller with the Autoconfigure option or as a secondary controller, the controller
module becomes inoperable and will need to be replaced.
The Redundant Controller setting (“view and edit Peripheral devices → Set
Peripheral Device Entry”) must remain enabled for single-controller
configurations. This preserves the default primary controller assignment of the
single controller.
■ In a single-controller configuration, disable the Write-Back Cache feature to avoid
the possibility of data corruption in the event of a controller failure. This will have
a negative effect on performance. To avoid either issue, use dual controllers.
Using two single-controllers in a clustering environment with host-based
mirroring provides some of the advantages of using a dual controller. However
you still need to disable the Write-Back Cache in case one of the single controllers
fails and you want to avoid the risk of data corruption. For this reason, a dual
controller configuration is preferable.
Note – For a single-controller configuration, the controller status shows “scanning,”
which indicates that the firmware is scanning for primary and secondary controller
status and redundancy is enabled even though it is not used. There is no
performance impact.
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