Managing CMM Directory Content CMM Files
OmniSwitch 6800/6850/9000 Switch Management Guide December 2007 page 4-9
Redundancy
CMM software redundancy is one of the switch’s most important fail over features. For CMM software
redundancy, at least two fully-operational OmniSwitch 6800 or OmniSwitch 6850 switches must be linked
together as a stack. However, with an OmniSwitch 9000, two fully-operational CMM modules must be
installed in the chassis at all times. In addition, the CMM software must be synchronized. (Refer to
“Synchronizing the Primary and Secondary CMMs” on page 4-27 for more information.)
In a stack of OmniSwitch 6800 or OmniSwitch 6850 switches, one of the switches has the primary role
and the another switch has the secondary role at any given time. (The primary and secondary roles are
determined by the switch number indicated on the LED on the front panel; the lowest number switch
becomes the primary switch in the stack.) The primary switch manages the current switch operations while
the secondary switch provides backup (also referred to as “fail over”).
Additional switches in a stack are set to “idle” for the purposes of redundancy. For more information on
managing a stack of switches, see the “Managing Stacks” chapter found in both the OmniSwitch 6800
Hardware Users Guide and the OmniSwitch 6850 Hardware Users Guide.
When two CMMs are running in an OmniSwitch 9000 switch, one CMM has the primary role and the
other has the secondary role at any given time. The primary CMM manages the current switch operations
while the secondary CMM provides backup (also referred to as “fail over”).
Redundancy Scenarios
The following scenarios demonstrate how the CMM software is propagated to other switches in a stack for
the purposes of coherent redundancy. In the examples below, W represents the working directory and C
represents the certified directory.
Scenario 1: Booting the Stack
The following diagram illustrates what occurs when a stack powers up. The stack displayed is a three
switch stack.
Powering Up a Stack
WC
WC
WC
1. Stack is pow-
ered up and boots
from the certified
directory.
2. The contents of
the certified direc-
tory of the primary
CMM switch are
copied to the
working directory
of the secondary
CMM switch.
The working
directory is then
copied to the certi-
fied directory.
3. The contents of
the certified direc-
tory of the pri-
mary
CMM
switch are copied
to the working
directory of addi-
tional switches.
The working direc-
tory is then copied
to the certified
directory.
Switch #1 Switch #2 Switch #3
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