Avago Technologies MegaRAID SAS 8204ELP - Manual (Page 18)

1-4 Overview
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external storage devices, which allow you to use a system that supports
enterprise-class SAS drives and desktop-class SATA II drives. Each
MegaRAID 1078-based SAS RAID controller can connect to drives
directly and can use expanders to connect to additional drives. Simplified
cabling between devices is an additional benefit.
These SAS controllers are based on the LSISAS1078 RAID On-a-Chip
(ROC) device. This device is compliant with the Fusion-MPT™
architecture and provides a PCI Express x4 or x8 interface.
Note: The MegaRAID SAS 8704ELP RAID controller and the
MegaRAID SAS 8704ELP RAID controller provide an x4
PCI Express interface. The MegaRAID SAS 8708EM2, the
MegaRAID SAS 8880EM2, and the MegaRAID SAS
8888ELP RAID controllers provide an x8 PCI Express
interface.
The LSISAS1078 ROC device provides an eight-lane, 2.5-Gbit/s PCI
Express host interface, eight 3.0 Gbit/s SAS or SATA ports, and a full-
featured, hardware-based RAID implementation. The LSISAS1078 ROC
device integrates a high-speed DDR/DDR2 SDRAM interface with a
hardware RAID assist engine for parity calculations. The LSISAS1078
ROC device provides the maximum benefits of a RAID system and
enables you to configure the system to satisfy your system requirements.
The LSISAS1078 ROC device increases system performance and
provides fault-tolerant data storage. The LSISAS1078 supports data
striping across multiple disks, which reduces disk access time because
multiple disks simultaneously read or write data. The LSISAS1078 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 SAS RAID controllers integrate eight high-performance SAS/SATA II
PHYs and a PCI Express bus master DMA core. Each of the eight PHYs
is capable of 3.0 Gbit/s SAS link rates and 3.0 Gbit/s SATA II link rates.
The LSISAS1078 ROC device adheres to the PCI Express Specification,
Revision 1.0a. The PCI Express software is backward compatible with
previous revisions of the PCI bus and PCI-X bus.