Huawei S Series White Paper page 33

S Series Switches
iStack Technology White Paper
Figure 2-21 Networking for smooth upgrade of a stack
A reliable stack can be divided into an active area and a backup area that back up each other.
After an upgrade starts, the two areas are upgraded in turn. When one area is upgrading,
traffic is transmitted in the other area.
A smooth upgrade undergoes three phases:
1.
2.
3.
If errors occur during a smooth upgrade, member switches in the stack can automatically roll
back to the original system version and set up a stack again.
Issue 01 (2013-05-25)
iStack
SwitchA
Building A
A command is executed in the stack to trigger a smooth upgrade. Members in the backup
area then restart with the new system software.
Members in the backup area set up an independent stack running the new system
software and notify members in the active area. The master switch in the backup area
starts to control the stack, and traffic is transmitted in the backup area. The active area
then starts the upgrade.
Members in the active area restart with the new system software and join the stack set up
by the members in the backup area. The master switch in the backup area displays the
upgrade result depending on the stack setup result.
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Building B
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2 Technology Description
SwitchB
Building C
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