HP A7143A RAID160 SA Controller Support Guide

RAID160 SA Controller Overview
Board Components and Features
Chapter 230
— vPars (HP-UX Virtual Partitions)
—Ignite UX
— Hot-pluggable disk drives
— Drive movement
— Adjustable stripe size
— S.M.A.R.T. disk drives
— Multiple online spares per array
— Background initialization
Overview of Array Accelerator Features
The array accelerator is a high performance, battery-backed, 100-MHz
SDRAM DIMM cache module.
The RAID160 SA controller uses cache to store read data from the disk
drives. The system can later access this read data. The controller
firmware uses the “read-ahead” and “most recently used” caching
algorithms.
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: