Juniper EX8208 Complete Hardware Manual page 71

Copyright © 2010, Juniper Networks, Inc.
Junos OS Release 10.1 or earlier—Consult Table 18 on page 43, Table 20 on page 44,
or Table 21 on page 44 to determine the number of power supplies needed (N). Then
multiple the N value by two.
NOTE: In Junos OS Release 10.1 or earlier, the power management feature
manages switches for N+1 redundancy only. This means, for example, that
power management raises an alarm if there is insufficient power to maintain
N+1 redundancy, but not if there is insufficient power to maintain N+N
redundancy.
Junos OS Release 10.2 or later—Consult Table 22 on page 46, Table 24 on page 46, or
Table 25 on page 47 in this section.
Starting with Junos OS Release 10.2, you can configure the power management software
to manage the switch power for N+N redundancy. When you configure power
management for N+N redundancy, power management lowers the maximum chassis
power consumption by lowering the maximum fan speed. It does so to compensate for
the extra power that is held in reserve in an N+N configuration than in an N+1 configuration,
because of which less power would ordinarily be available to power line cards. By reducing
the maximum chassis power consumption, power management allows the switch to
power more line cards.
The configuration type of the switch and the input voltage determine the number of
power supplies needed (N) for the switch. You must then install additional power supplies
to meet the N+N redundancy configuration. For details about different switch
configurations, see "EX8208 Switch Configurations" on page 7 or EX8216 Switch
Configurations.
The tables in this section list the N+N power requirements for different EX8200 switch
configurations:
Table 22 on page 46—Lists the N+N power requirements of EX8208 switch
configurations that use 2000 W AC power supplies.
Table 23 on page 46—Lists the N+N power requirements of EX8208 switch
configurations that use 3000 W AC power supplies.
Table 24 on page 46—Lists the N+N power requirements of EX8216 switch
configurations that use 2000 W AC power supplies.
Table 25 on page 47—Lists the N+N power requirements of EX8216 switch
configurations that use 3000 W AC power supplies.
Chapter 2: Component Descriptions
45