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RAID Overview 2-11
Copyright © 2002 by LSI Logic Corporation. All rights reserved.
2.3.14 Disk Array Types
Table 2.4 describes the RAID disk array types.
2.3.15 Enclosure Management
Enclosure management is the intelligent monitoring of the disk
subsystem by software and/or hardware.
The disk subsystem can be part of the host computer or can be separate
from it. Enclosure management helps you stay informed of events in the
disk subsystem, such as a drive or power supply failure. Enclosure
management increases the fault tolerance of the disk subsystem.
Table 2.4 Disk Array Types
Type Description
Software-
Based
The array is managed by software running in a host computer
using the host CPU bandwidth. The disadvantages associated
with this method are the load on the host CPU and the need
for different software for each operating system.
SCSI to SCSI The array controller resides outside of the host computer and
communicates with the host through a SCSI adapter in the
host. The array management software runs in the controller. It
is transparent to the host and independent of the host
operating system. The disadvantage is the limited data transfer
rate of the SCSI channel between the SCSI adapter and the
array controller.
Bus-Based The array controller resides on the bus (for example, a PCI or
EISA bus) in the host computer and has its own CPU to
generate the parity and handle other RAID functions. A bus-
based controller can transfer data at the speed of the host bus
(PCI, ISA, EISA, VL-Bus) but is limited to the bus it is designed
for. MegaRAID SCSI 320-0 resides on a PCI bus, which can
handle data transfer at up to 132 Mbytes/s. With MegaRAID
SCSI 320-0, the channel can handle data transfer rates up to
320 Mbytes/s per SCSI channel.