HP A7143A RAID160 SA Controller Support Guide, February 2007

RAID160 SA Controller Overview
Board Components and Features
Chapter 2
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The RAID160 SA controller also uses cache to complete drive write operations more quickly. This use of the
cache has further performance benefits:
• If the system requires data that still resides in the write cache, the controller delivers this data from the
cache. This process is quicker than delivering the data from a drive.
• If the system writes new data to the same location, the controller overwrites the cache contents. This
eliminates a drive write operation.
• If the system performs a RAID 1 procedure, the controller gets mirrored data from the cache instead of
from host memory.
• If the system performs a RAID 5 procedure, the write cache collects enough data blocks from several write
accesses to carry out a full stripe write to the disk drives. This operation eliminates the need to calculate
and update parity information each time a data block is written to the drive.
Other features of the array accelerator include:
• Cache capacity of 256-MB with 224-MB usable cache (32 MB of the cache is used for transfer buffer).
• Error checking and correcting (ECC) memory, providing single-bit data correction.
Batteries
The array accelerator cache has two NiMH battery packs.
Figure 2-3 Battery Packs
If a power outage occurs, the batteries will preserve cashed data for up to 72 hours. When power is restored to
the system, an initialization process will write the preserved data to the disk drives.
The batteries are continuously recharged using a trickle-charging process whenever the system power is on.