Active-Passive Mode - Adaptec DURASTOR 6320SS Manual

Active-Passive Mode

In active-passive mode, there is one active and one passive RAID
controller. The primary (active) controller operates with both of its
host ports enabled and presents all LUNs on both ports to
maximize bandwidth. The secondary (passive) controller keeps
both of its host ports passive, and does not service any LUNs. Both
controllers monitor each other's heartbeats and the passive
controller receives write data and parity logs from the active
controller.
If the active controller fails, normal fail-over occurs to the passive
controller, which becomes active by enabling both of its host ports
and takes ownership of all arrays.
Table A-4 Presentation of LUNs in Active-Passive Mode
Controller 1
Controller Host Port 0
Status (FC1)
Both Controller 1
controllers LUNs
online
Controller 1 Inactive
failed
Controller 2 Controller 1
failed LUNs
Controller 1 is the default active controller. Controller 2 is always
passive unless controller 1 fails. The default active controller is not
selectable.
Because the active controller does not have to mirror the passive
controllers data, more write-back cache memory can be made
available to the active controller. This means that half the cache
memory can be dedicated to writes and half to reads. This is the
same allocation used in stand-alone mode.
Controller 1 Controller 2
Host Port 1 Host Port 0
(FC2) (FC1)
Inactive Inactive
Inactive Controller 1
LUNs
Controller 2 Inactive
LUNs
Theory of Controller Operation
Controller 2
Host Port 1
(FC2)
Controller 2
LUNs
Controller 2
LUNs
Inactive
A-11