4
Step 3: Determine the level of
redundant power desired.
See Table 2 for definitions of the different
levels of redundancy.
No redundancy: Skip to Step 4.
System power redundancy: System power is
the power needed to run the switching and
routing functionality in the switch—
essentially everything except PoE. One power
supply is sufficient for full system power for
the ProCurve Switch 5406zl chassis; two
power supplies are required for the ProCurve
Switch 8212zl/5412zl. Full system power
redundancy is achieved with two power
supplies for the 5406 and four power supplies
for the 8212/5412.
Since there are only 2 power supply slots in
the 5406, system power N+1 redundancy and
full redundancy are equivalent. The 8212/
5412 can have system power N+1 with three
supplies and full redundancy with four
supplies.
Non-redundant power
N+1 redundancy
Full redundancy
No power is held in reserve. For system power, if a power supply fails, some or all parts of the
switch become inoperative. For PoE power, all power supplied by the available supplies can be
used to power PDs. If a power supply fails, the amount of PoE power supplied by the failed
supply is no longer available. The switch will turn off the number of PDs starting with the
lowest PoE priority PD up to the wattage lost with the failed supply.
For system power, one supply can fail and the entire switch remains functional. For PoE power, one
power supply can fail without loss of power to any currently powered device. Under N+1, the
switch will hold in reserve (not use) the amount of PoE power equal to the largest PoE supply. If a
power supply fails, the reserve power is used to continue to power all PDs without interruption.
N+1 redundancy may not protect against a failed external power main.
For system power, one half of the power supplies can fail and the entire switch remains
functional. For PoE power, one half of the power supplies can fail without power interruption to
any connected nodes. The switch will hold at least one half of the PoE power available from all
supplies in reserve to be used in case of power supply failures. Full redundancy would be used if
protection from a failed external power main is desired.
Definitions of redundant power
Table 2. Redundant power definitions
PoE power redundancy: PoE power is the
power necessary to power the external PDs
connected to the switch. PoE power is
independent from system power and is not
used in powering the normal functions of
the switch.
Determine the level of PoE power redundancy
you desire. Table 2 has definitions for the
different types of redundant power.
Currently, the switch does not automatically
hold any PoE power in reserve for redundancy.
Plan for the amount of power to be held in
reserve, and keep the wattage needed for the
level of redundancy desired in reserve by
controlling the number of PDs on the switch.
