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What are Primary controller and Secondary controller?
The Primary and Secondary controllers are used to serve the host
computer's I/O requests. Take note that the configurations and
settings can only be done on the Primary controller. The Secondary
controller then synchronizes the configuration information of the
Primary controller, making the configurations of the Primary and
Secondary controllers exactly the same.
The controllers continuously monitor each other. When a controller
detected that the other controller is not responding, the working
controller will immediately take over and disable the failed controller
until it has been replaced and enabled by user command.
When should I choose Primary, Secondary or Autocfg mode?
Generally Autocfg is the simplest way to configure the controllers. By
setting each controller to Autocfg mode, the controllers will decide
among themselves which will be the Primary or Secondary controller.
If you need to specify a particular controller as Primary or Secondary,
you must set this manually.
Limitations
Both controllers must use the same firmware version.
The time of the takeover process is about 5 seconds. Some
operating systems will not retry accessing the HDDs.
The cache memory will switch to Write-Through mode.
In firmware versions earlier than 2.11, only the primary controller
serves the host's I/O request while the secondary controller just
monitors the primary controller continuously. In firmware version
2.11 or later, both controllers can serve the host's I/O request.
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User's Guide
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