Infortrend EonStor DS S12 Series Hardware Manual page 15

EonStor DS S12/S16/S24 Series Hardware Manual
The top controller (Controller A) is the primary controller which manages the entire
RAID system in normal operations. The bottom controller (Controller B) is the
secondary (= redundant) controller which is idle during normal operation and takes
over the management role when Controller A cannot function properly due to
hardware error, controller module removal, etc.
If the failed Controller A restarts or a replacement is installed, Controller A will
temporarily assume the role of the secondary controller.
When the RAID subsystem is rebooted, all system configurations revert to the default
state and Controller B returns the primary role to Controller A.
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