Texas Memory Systems RamSan-300/320 - Manual (Page 78)

Primary (Active, Secondary is X)
This state is identical to “Primary (Active)” state with one
important difference: the administrator has selected a secondary
controller, Controller X, to backup this primary controller. If this
primary controller loses its link for an extended period or cannot
transmit data for any reason, the secondary controller mimics the
failed controller, preventing performance loss.
To get a controller into this state: First, configure the primary
controller as “Primary (Active).” Then, from the secondary
controller’s setup menu, set the secondary controller’s high
availability to “Secondary (Passive, Primary is X)” state and choose
the primary controller as the primary.
Note: Once the administrator sets a controller as a primary
controller with a backup, it must remain primary until the
administrator changes the secondary controller’s configuration
from secondary to primary.
Secondary (Passive, Primary is X)
This state is the sets the controller as secondary to a primary
controller, as mentioned in the section above. To set a controller
in this state, first configure its high availability to “Secondary
(Passive, Primary is X)” state from the “Primary (Active)” state.
The controller remains in this state until the administrator
configures it back to “Primary (Active)” state or until a failover
occurs. If a failover occurs, the system copies all of the attributes
of the primary controller to the secondary controller and activates
its links. From this state, all of the secondary controller’s
attributes are meaningless and are not updateable until the
administrator sets the controller back to “Primary (Active)” state.
Primary (Passive, Secondary is X)
This state indicates that the primary controller has experienced a
failure; however, often these failures are not fatal and are
recoverable. For example, if a cable is pulled for an extended
period, the link “fails,” but once the controller is plugged back in,
the link becomes usable again. Since the system copies all
attributes of a failed primary controller to the secondary, the
system cannot allow the failed primary controller to come back
online. Instead, the system disables the links, and the original
primary controller becomes a backup for the active secondary
controller. The administrator cannot set this controller back to an
active state directly. To re-activate this controller, either the
secondary controller must fail, or the administrator must re-
configure the secondary controller to “Primary (Active)” state.
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