IBM ServeRAID M5025, User Manual

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1-4 Overview
1.3 General Description
The ServeRAID M5025 controller brings 6.0 Gbit/s Serial Attached SCSI
(SAS) and 3.0 Gbit/s Serial ATA II (SATA II) performance to host
adapter, workstation, and server designs. The controller supports
external storage devices, which allows you to use a system that supports
enterprise-class SAS drives, and desktop-class SATA II drives. Each
ServeRAID M5025 controller can connect to drives directly. Simplified
cabling between devices is an additional benefit.
This controller is based on the LSISAS2108 ROC device. This device is
compliant with the Fusion-MPT architecture and provides a PCI Express
x8 interface.
The controller integrates eight high-performance SAS/SATA II PHYs and
a PCI Express bus master DMA core. Each of the eight PHYs is capable
of 6.0 Gbit/s SAS link rates and 3.0 Gbit/s SATA II link rates.
The LSISAS2108 ROC device provides an eight-lane, 5-Gbit/s PCI
Express host interface, eight 6.0 Gbit/s SAS ports or 3.0 Gbit/s SATA
ports, and a full-featured, hardware-based RAID implementation. The
LSISAS2108 ROC device integrates a high-speed DDR/DDR2 SDRAM
interface with a hardware RAID assist engine for parity calculations. The
LSISAS2108 ROC device provides the maximum benefits of a RAID
system and enables you to configure the system to satisfy your system
requirements.
The LSISAS2108 ROC device increases system performance and
provides fault-tolerant data storage. The LSISAS2108 supports data
striping across multiple disks, which reduces disk access time because
multiple disks simultaneously read or write data. The LSISAS2108 ROC
device backs up data with either data mirroring or a parity block. Either
backup method enables you to recover lost data in the event of a disk
failure. You can select the data backup method that best suits your
needs. A hardware RAID assist exclusive-OR (XOR) engine speeds
parity generation and checking and reduces system-access times.
The controller supports the SAS protocol as described in the Serial
Attached SCSI Standard , version 1.1 . In addition, it supports the Serial
ATA II (SATA II) protocol defined by the Serial ATA Specification,
Version 1.0a , and the Serial ATA II; Extension to the Serial ATA