IBM ServeRAID-MR10is, Руководство пользователя

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ServeRAID-MR10is VAULT SAS/SATA Controller User’s Guide 4-1
Chapter 4
Introduction to the
Intelligent Backup Bat-
tery Unit
IBM
®
provides the ServeRAID-MR10is intelligent Battery Backup Unit
(iBBU) on its high-performance ServeRAID-MR10is SAS/SATA
Controller. The iBBU protects the integrity of the cached data on RAID
controller by providing backup power if there is a complete AC power
failure or a brief power outage. The iBBU provides an inexpensive
alternative to using an uninterruptible power supply (UPS).
Writing a block of data to cache memory is much faster than writing it to
a storage device. The ServeRAID-MR10is controller then writes the
cached data to the storage device when system activity is low or when
the cache is getting full. The risk of using write-back cache is that the
cached data can be lost if the AC power fails before it has been written
to the storage device.
4.1 Functionality
An intelligent BBU has built-in functionality to charge the battery pack
automatically and to communicate battery status information such as
voltage, temperature, and current, to the host computer system.
The iBBU is compatible with systems that offer auxiliary power. Battery
charging and recharging take place automatically. The battery in the
iBBU must recharge for at least six hours under normal operating
conditions. To protect your data, the firmware changes the Write Policy
to
write-through until the battery unit is sufficiently charged. When the
battery unit is charged, the controller firmware changes the Write Policy
to
write-back to take advantage of the performance benefits of data
caching.
The iBBU monitors the voltage level of the DRAM modules installed on
the ServeRAID-MR10is controller. If the voltage drops below a
predefined level, the battery backup module switches the memory power