American Megatrends MegaRAID Express 500 - Manual (Page 21)

Chapter 2 Introduction to RAID 7
MegaRAID Express 500 – Host-Based RAID Solution
RAID products are either:
•
host-based or
•
SCSI-to-SCSI
The MegaRAID Express 500 controller is a host-based RAID solution.
MegaRAID Express 500 is a PCI adapter card that is installed in any available
PCI expansion slot in a host system.
Host-Based A host-based RAID product puts all of the RAID intelligence on an adapter card
that is installed in a network server. A host-based RAID product provides the
best performance. MegaRAID Express 500 is part of the file server, so it can
transmit data directly across the computer’s buses at data transfer speeds up to
132 MB/s.
The available sequential data transfer rate is determined by the following factors:
•
the sustained data transfer rate on the motherboard PCI bus
•
the sustained data transfer rate on the i960RM PCI to PCI bridge
•
the sustained data transfer rate of the SCSI controller
•
the sustained data transfer rate of the SCSI devices
•
the number of SCSI channels
•
the number of SCSI disk drives
Host-based solutions must provide operating system-specific drivers.
SCSI-to-SCSI A SCSI-to-SCSI RAID product puts the RAID intelligence inside the RAID
chassis and uses a plain SCSI Host Adapter installed in the network server. The
data transfer rate is limited to the bandwidth of the SCSI channel. A SCSI-to-
SCSI RAID product that has two wide SCSI channels operating at speeds up to
160 MB/s must squeeze the data into a single wide SCSI (160 MB/s) channel
back to the host computer.
In SCSI-to-SCSI RAID products, the hard drive subsystem uses only a single
SCSI ID, which allows you to connect multiple drive subsystems to a single
SCSI controller.