EMC Symmetrix DMX-3, Product Manual

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Reliability and availability features 171
Data Integrity, Availability, and Protection
Power Zone Task Symmwin has a Power Zone Task which is disabled by default. The
Power Zone Task is optional under normal operation, however it is
highly recommended and considered best practice to disable the task
before beginning any power- related maintenance on the system or
site. The task setting can be modified in the Symmetrix Site
Configuration window. An online configuration change is not
required to change this setting.
When the Power Zone Task is enabled and the system loses AC
power to a single power zone, a 20-hour timer is invoked. The system
will call home to notify the EMC Customer Support Center of the
event. When the timer counts down to five hours the system will
again call home. Before the 20-hour period ends, the EMC customer
engineer can choose one of three options:
◆
Repair the cause of the power fault.
◆
Reset the 20-hour timer to continue the single power zone
operation.
◆
Allow the system to vault, shutting down the system in an
orderly manner.
Battery backup
units The BBU modules ensure data integrity during power outages. The
BBU modules provides the means for vaulting fast-write data that
might be in global memory if AC power is lost on both lines to the
unit. In addition to providing nonvolatility to the Symmetrix system,
the BBU modules are fully capable of powering not only all electronic
components, but also all HDAs during this time. This capability
eliminates emergency power off situations, meaning that the disks
are always powered down in an orderly manner, extending their
useful life considerably.
The BBU modules allow the Symmetrix system to remain online to
the host system in the event of an AC power loss. The BBU modules
automatically turn on when the Symmetrix system detects loss of AC
power. The BBU modules will maintain power to the Symmetrix
system for up to five minutes while the global memory is vaulted to
the vault disk drives.
The BBU modules also prevent disk drive failures due to the sharp
power drops that occur during unexpected power interrupts. The
BBU modules have sufficient capacity to ride out multiple AC
outages, however it requires up to eight hours of uninterrupted
recharge time to fully recharge the BBU modules. The BBU modules
also contain a self-diagnostic controller to ensure availability and