ServeRAID M5025 SAS/SATA Controller User’s Guide
4-1
Chapter 4
Introduction to the
Intelligent Battery
Backup Unit
The intelligent Battery Backup Unit (iBBU) is for use with its high-
performance ServeRAID M5025 SAS/SATA controller. The battery
backup unit protects the integrity of the cached data on 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 M5025 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. This risk factor is eliminated when the controller
has an onboard iBBU.
The iBBU monitors the voltage level of the DRAM modules installed on
the ServeRAID M5025 controller. If the voltage drops below a predefined
level, the battery backup module switches the memory power source
from the controller to the battery pack attached to the iBBU. As long as
the voltage level stays below the predefined value, the iBBU provides
power for memory. If the voltage level returns to an acceptable level, the
iBBU switches the power source back to the controller, and all
incomplete writes to storage devices are completed with no data loss.
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.
Summary of Contents for ServeRAID M5025
Page 1: ...ServeRAID M5025 SAS SATA Controller USER S GUIDE S e p t e m b e r 2 0 1 1...
Page 12: ...xii Contents...
Page 14: ...xiv Contents...
Page 16: ...xvi Contents...
Page 48: ...3 8 ServeRAID M5025 SAS SATA Controller Characteristics...
Page 78: ...A 4 Notices...
Page 84: ...B 6 Glossary of Terms and Abbreviations...
Page 85: ......
Page 86: ...Part number 60Y1428...