Dell PowerEdge VRTX Chassis Management Controller Version 1.0 for Dell PowerEd - Page 147

Default Redundancy Configuration, AC Redundancy

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To operate remaining PSUs at their maximum efficiency, use the following power redundancy modes: • PSU Redundancy mode with DPSE provides power efficiency. At least two supplies are online, with one PSU required to power the configuration, and one to provide redundancy in case of a PSU failure. PSU Redundancy mode offers protection against the failure of any one PSU, but offers no protection in the event of an AC grid loss. • AC Redundancy mode with DPSE, where at least two PSUs are active, one on each power grid. AC redundancy also balances the efficiency and maximum availability for a partially-loaded modular enclosure configuration. • Disabling DPSE provides the lowest efficiency as all six supplies are active and share the load, resulting in lower utilization of each power supply. DPSE can be enabled for all two power supply redundancy configurations explained above - Power Supply Redundancy, and AC Redundancy. NOTE: In a two PSU configuration modes, server load may prevent any PSU from changing to the Standby mode. • In a Power Supply Redundancy configuration, in addition to the PSUs required to power the enclosure, the enclosure always keeps an additional PSU powered on and marked Online. Power utilization is monitored and one PSU can be moved to Standby state on the basis of overall system load. In a four PSU configuration, a minimum of two PSUs are always turned on. Because an enclosure in the Power Supply Redundancy configuration always has an extra PSU engaged, the enclosure can accommodate the loss of one online PSU and still have enough power for the installed server modules. The loss of the online PSU causes a standby PSU to come online. Simultaneous failure of multiple PSUs may result in the loss of power to some server modules while the standby PSUs are turning on. • In AC Redundancy configuration, all PSUs are engaged when the chassis is turned on. Power utilization is monitored, and if system configuration and power utilization allows, PSUs are moved to the Standby state. Because the Online status of PSUs in a grid mirrors that of the other grid, the enclosure can sustain the loss of power to an entire grid with no interruption of power to the enclosure. An increase in power demand in the AC Redundancy configuration cause the engagement of PSUs from the Standby state. This maintains the mirrored configuration needed for dual-grid redundancy. NOTE: With DPSE in enabled state, if power demand increases in both the two Power Redundancy policy modes, the standby PSUs are brought Online to reclaim power. Default Redundancy Configuration As shown in the table here, the default redundancy configuration for a chassis depends on the number of PSUs that it contains. Table 28. Default Redundancy Configuration PSU Configuration Default Redundancy Policy Default Dynamic PSU Engagement Setting Two PSUs DC Redundancy Disabled Four PSUs DC Redundancy Disabled AC Redundancy In AC redundancy mode with four PSUs, all four PSUs are active. The two PSUs must connect to one AC power grid, while the other two PSUs are connect to the other AC power grid. CAUTION: To avoid a system failure, and for AC redundancy to work effectively, there must be a balanced set of PSUs properly cabled to separate AC grids. If one AC grid fails, the PSUs on the functioning AC grid take over, without interrupting the servers or infrastructure. 147

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To operate remaining PSUs at their maximum efficiency, use the following power redundancy modes:
•
PSU Redundancy
mode with DPSE provides power efficiency. At least two supplies are online, with one PSU
required to power the configuration, and one to provide redundancy in case of a PSU failure. PSU Redundancy
mode offers protection against the failure of any one PSU, but offers no protection in the event of an AC grid
loss.
•
AC Redundancy
mode with DPSE, where at least two PSUs are active, one on each power grid. AC redundancy
also balances the efficiency and maximum availability for a partially-loaded modular enclosure configuration.
•
Disabling DPSE provides the lowest efficiency as all six supplies are active and share the load, resulting in lower
utilization of each power supply.
DPSE can be enabled for all two power supply redundancy configurations explained above —
Power Supply
Redundancy
, and
AC Redundancy
.
NOTE:
In a two PSU configuration modes, server load may prevent any PSU from changing to the Standby mode.
•
In a
Power Supply Redundancy
configuration, in addition to the PSUs required to power the enclosure, the
enclosure always keeps an additional PSU powered on and marked
Online
. Power utilization is monitored and
one PSU can be moved to Standby state on the basis of overall system load. In a four PSU configuration, a
minimum of two PSUs are always turned on.
Because an enclosure in the
Power Supply Redundancy
configuration always has an extra PSU engaged, the
enclosure can accommodate the loss of one online PSU and still have enough power for the installed server
modules. The loss of the online PSU causes a standby PSU to come online. Simultaneous failure of multiple
PSUs may result in the loss of power to some server modules while the standby PSUs are turning on.
•
In
AC Redundancy
configuration, all PSUs are engaged when the chassis is turned on. Power utilization is
monitored, and if system configuration and power utilization allows, PSUs are moved to the
Standby
state.
Because the
Online
status of PSUs in a grid mirrors that of the other grid, the enclosure can sustain the loss of
power to an entire grid with no interruption of power to the enclosure.
An increase in power demand in the
AC Redundancy
configuration cause the engagement of PSUs from the
Standby
state. This maintains the mirrored configuration needed for dual-grid redundancy.
NOTE:
With DPSE in enabled state, if power demand increases in both the two Power Redundancy policy
modes, the standby PSUs are brought
Online
to reclaim power.
Default Redundancy Configuration
As shown in the table here, the default redundancy configuration for a chassis depends on the number of PSUs that it
contains.
Table 28. Default Redundancy Configuration
PSU Configuration
Default Redundancy Policy
Default Dynamic PSU Engagement Setting
Two PSUs
DC Redundancy
Disabled
Four PSUs
DC Redundancy
Disabled
AC Redundancy
In AC redundancy mode with four PSUs, all four PSUs are active. The two PSUs must connect to one AC power grid,
while the other two PSUs are connect to the other AC power grid.
CAUTION: To avoid a system failure, and for AC redundancy to work effectively, there must be a balanced set of
PSUs properly cabled to separate AC grids.
If one AC grid fails, the PSUs on the functioning AC grid take over, without interrupting the servers or infrastructure.
147