Maintenance Discharge Cycles - IBM Storwize V7000 Unified Problem Determination Manual

charge to support a saving of critical data. This situation happens when, for
example, both batteries have two-thirds of a charge. The total charge that is
available in the enclosure is sufficient to support a saving of critical data once;
therefore, both canisters are in active state and I/O operations are permitted. If one
battery fails though, the remaining battery has only two-thirds of a charge, and the
total charge that is available in the enclosure is now insufficient to perform a
saving of the critical data if the ac power fails. Data protection cannot be
guaranteed in this case. The nodes save the critical data by using the ac power and
enter service state. The nodes do not handle I/O operations until the remaining
battery has sufficient charge to support the saving of the critical data. When the
battery has sufficient charge, the system automatically restarts.
Important: Although Storwize V7000 Unified is resilient to power failures and
brown outs, always install Storwize V7000 Unified in an environment where there
is reliable and consistent ac power that meets the Storwize V7000 Unified
requirements. Consider uninterruptible power supply units to avoid extended
interruptions to data access.

Maintenance discharge cycles

Maintenance discharge cycles extend the lifetime of the batteries and ensure that
the system can accurately measure the charge in the batteries. Discharge cycles
guarantee that the batteries have sufficient charge to protect the Storwize V7000
Unified system.
Maintenance discharge cycles are scheduled automatically by the system and
involve fully discharging a battery and then recharging it again. Maintenance
discharges are normally scheduled only when the system has two fully charged
batteries. This condition ensures that for the duration of the maintenance cycle, the
system still has sufficient charge to complete a save of the critical data if the ac
power fails. This condition also ensures that I/O operations continue while the
maintenance cycle is performed. It is usual for both batteries to require a
maintenance discharge at the same time. In these circumstances, the system
automatically schedules the maintenance of one battery. When the maintenance on
that battery completes, the maintenance on the other battery starts.
Maintenance discharges are scheduled for the following situations:
v A battery has been powered on for three months without a maintenance
v A battery has provided protection for saving critical data at least twice.
v A battery has provided protection for at least 10 brown outs, which lasted up to
A maintenance discharge takes approximately 10 hours to complete. If the ac
power outage occurs during the maintenance cycle, the cycle must be restarted.
The cycle is scheduled automatically when the battery is fully charged.
Under the following conditions, a battery is not considered when calculating
whether there is sufficient charge to protect the system. This condition persists
until a maintenance discharge cycle is completed.
v A battery is performing a maintenance discharge.
v A battery has provided protection for saving critical data at least four times
v A battery has provided protection for at least 20 brown outs, which lasted up to
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Storwize V7000 Unified: Problem Determination Guide Version
discharge.
10 seconds each.
without any intervening maintenance discharge.
10 seconds each.