Hitachi Virtual Storage Platform, Руководство пользователя и справочник

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Power On/Off Procedures
4–5
Hitachi VSP User and Reference Guide
Power on procedure after emergency power off
To power up the VSP storage system after emergency shutdown, reverse
the emergency power off procedure.
1. In all system racks, turn on the circuit breakers in the PDUs that power
the drive units.
2. In both controller racks, turn on the circuit breakers in the PDUs that
power the controllers.
3. Follow the instructions in Normal Power On/Off procedures on page 4-3 .
Battery backup operations
The Virtual Storage Platform is designed so that it cannot lose data or
configuration information if the power fails. The battery system is designed
to provide enough power to completely destage all data in the cache if two
consecutive power failures occur and the batteries are fully charged. If the
batteries do not contain enough charge to provide sufficient time to destage
the cache when a power failure occurs, the cache operates in write through
mode. This synchronously writes to HDDs to prevent slow data throughput
in the cache. When the battery charge is 50% or more, the cache write
protect mode operates normally.
When a power failure occurs and continues for 20 milliseconds or less, the
storage system continues normal operation. If the power failure exceeds 20
milliseconds, the storage system uses power from the batteries to back up
the cache memory data and storage system configuration data to the cache
flash memory on each cache board. This continues for up to ten minutes.
The flash memory does not require power to retain the data.
The following illustration shows the timing in the event of a power failure.
Figure 4-1 Battery Backup Operations
Item Description Item Description
Power failure occurs The storage system continues to operate
for 20 milliseconds and detects the power
failure.
The cache memory data and the storage
system configuration are backed up to
the cache flash memory on the cache
boards. The backup continues even if
power is restored during the backup. Unrestricted data backup. Data is
continuously backed up to the cache
flash memory.