Hitachi G1500 - Chapter 7: VSP G1 x00 and F1 x00 Batteries; Battery Backup Operations

Chapter 7: VSP G1x00 and F1x00 batteries
The batteries temporarily provide the storage system with power to maintain its caching
operation during a power failure event. The following information describes the battery
life expectancy, battery operation, and cache backup process. Also, some specic
guidelines are provided for storing the system during an extended period of time non-
oper
ation.
Battery backup operations
The stor
age system is designed to r
etain data and conguration information when the
po
wer fails. The battery system can provide sucient power with fully charged batteries
to completely back up all data in the cache if two consecutive power failures occur. If the
batteries do not contain enough charge to provide sucient time to back up the cache
when a power failure occurs, the cache operates in write-through mode and writes
directly to the drives to prevent slow data throughput via the cache. When the battery
charge is 50% or more, the cache write through mode is turned o and the system
operates normally.
If a power failure occurs and continues for up to 20 milliseconds, the storage system
continues normal operation. If the power failure exceeds 20 milliseconds, the storage
system uses power from the batteries to keep the cache active while the system copies
the storage system conguration and cached data to the cache ash memory in the
cache backup modules. The process continues up to 32 minutes. The cache ash drives
do not require power to retain the data.
The following illustration shows the timing if a power failure occurs.
Item Description
1 Power failure occurs.
Chapter 7: VSP G1x00 and F1x00 batteries
Hitachi Virtual Storage Platform G1000, G1500, and VSP F1500 Hardware Guide 125