Disk Array Types
The RAID disk array types are listed in the following table:
| Type | Description |
|
| Software- | The array is managed by software running in a host computer using |
|
| Based | 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. |
|
The array controller resides on the bus (for example, a PCI or |
| ||
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| EISA bus) in the host computer and has its own CPU to generate |
|
|
| the parity and handle other RAID functions. A |
|
|
| 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 |
|
|
| Express 500 resides on a PCI bus, which can handle data transfer |
|
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| at up to 132 MB/s. With MegaRAID Express 500, the channel can |
|
|
| handle data transfer rates up to 160 MB/s per SCSI channel. |
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|
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|
|
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 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.
16MegaRAID Express 500 Hardware Guide