Cache Backup Batteries - Hitachi G1500 Hardware Manual

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Cache backup batteries

If a power failure occurs, nickel-hydride batteries keep the cache memory active while
the entire storage system configuration and data in the cache are copied to the flash
memory in the cache backup modules. The batteries are located in the cache backup
modules. They are fully charged at the distribution center where the storage system is
assembled and tested. During shipment, the batteries are disconnected automatically to
prevent any discharging during shipping and storage until the system is installed. During
installation, they are reconnected. The following figure provides an overview of the cache
backup battery.
Note: The storage system generates a SIM when the cache backup batteries
are not connected.
Hitachi Virtual Storage Platform G1000, G1500, and VSP F1500 Hardware Guide
The storage system continues to operate for 20 milliseconds and
detects the power failure.
The cache memory data and storage system configuration are backed
up to the cache flash memory in the cache backup assemblies. If power
is restored during the backup, the backup stops unless the backup
battery capacities are used less than 50%. In case, the system operates
in write-through mode until the batteries are charged enough for a full
backup.
Data is stored in the cache flash memory until power is restored, and
then it is written to the drives.
Chapter 7: VSP G1x00 and F1x00 batteries
Cache backup batteries
Description
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