Dell PowerConnect J-EX8208, Software Manual

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Power Priority of Line Cards
Power management powers line cards on or off based on the power priority of the slots
they occupy:
•
When a switch powers on, power management provides power to the line cards in the
order of their slot priority, with line cards in high priority slots receiving power first. Thus
if available power (including redundant power) is exhausted before all line cards receive
power, higher priority cards are powered on while lower priority cards remain powered
off.
• If the switch starts receiving insufficient power because of power supply failure or some
other problem, power management powers off the line cards in reverse-priority order
until power (including redundant power) is sufficient for the remaining cards. Thus
higher priority line cards are more likely to retain power in power shortage conditions
than are lower priority line cards.
• Power management responds to changes in power availability and line card operating
status by powering line cards on or off as appropriate. For example, if you add a power
supply, lower priority cards that were powered off due to insufficient power are powered
on in priority order.
If you take a line card offline, power management no longer allocates power to it. If
power to the switch is insufficient when you take a line card offline, power management
allocates the freed power to a lower priority card that was offline due to lack of power
and brings it online. Restarting a line card, however, does not affect the power allocated
to it. Thus when power is insufficient, restarting a line card does not change its operating
status or the operating status of other line cards.
NOTE: Because power management does not allocate power to an offline
line card, a line card that has been taken offline in a J-EX8200 switch is
not automatically brought online when you commit a configuration. You
must explicitly bring the line card online with the
request chassis fpc slot
slot-number online
command. This behavior differs from other platforms
running the Junos OS, which automatically bring an offline FPC online when
you commit a configuration.
The actual power priority of a slot is determined first by the slot’s assigned priority and
second by the slot’s number. If more than one slot has the same assigned priority, power
priority is determined by slot number, with the lowest-numbered slots receiving power
first.
By default, all slots are assigned the lowest priority. You can assign a priority to a slot
using the CLI. If you do not explicitly assign priorities to slots, the slots receive power in
ascending order of slot numbers.
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Chapter 18: Power Management Overview