Hardware User's Guide

4 Intel® RAID Controller RS25SB008 Hardware User’s Guide
• Smart initialization automatically checks consistency of virtual disks if there are five
or more disks in a RAID 5 array, which optimizes performance by enabling read-
modify-write mode. RAID 5 arrays of only three or four drives use Peer Read mode.
• Smart Technology predicts failures of drives and electronic components.
• Patrol Read checks drives and maps bad sectors.
• Commands are retried at least four times.
• Firmware provides best effort to recognize an error and recover if possible.
• Failures are logged from controller and drive firmware, and SMART monitor.
• Failures are logged in NVRAM, viewable from OS Event Log, Intel
®
RAID Web
Console 2, CIM, and LEDs.
• Multiple cache options allow configuration-specific performance optimization:
— Write-back: Faster because it does not wait for the disk but data will be lost if
power is lost.
— W
rite-through: Usually slower but ensures data is on the disk.
— Read Ahead: Predicts next read will
be sequential and buffers this data into
the cache.
— Non
Read Ahead: Always reads from the drive after determining exact location
of each read.
— Adaptive Read Ahead: Read
s ahead and caches data only if doing
sequential reads.
— I/O setting. Determines whether read operat
ions check the cache before reading
from disks.
✧ Cache I/O:
Checks cache first, only reads disk if data is not in the cache.
✧ Direct I/O: Reads da
ta directly from disk. (not cache)
• Redundancy through:
— Configuration stored in non-volatile RAM and on the drives (COD).
— Hot-swap support.
— Super Cap 2 backup for cache memory.