Working with SCSI Storage Devices
Termination
The Importance of SCSI Bus Termination
All host adapters and the SCSI devices attached to them must be properly terminated, or they will not work reliably. Different SCSI devices are terminated in different ways. Some SCSI devices require users to manually insert or remove the terminators while others have built-in terminators that are enabled or disabled via switches or software commands. SCSI termination is an important part of any SCSI enhanced storage system.
Termination implies the use of resistors within the devices at each end of the bus. Termination is not required in other devices on the bus. Termination is a necessary for ensuring that all commands and data can be transmitted to and from all devices on the bus without error. Without proper termination, signals can be reflected across the bus causing devices to incorrectly respond to specific commands or incorrectly store and retrieve data.
Connecting for Performance - Getting the most from multi-device SCSI environments
Bus Segmentation
When connecting SCSI peripherals of varying interface types, it is important to consider the effects each will have on the overall transfer rate of the bus. When a host SCSI card establishes communication with peripheral devices, it will set the maximum transfer rate of the bus to match the slowest connected device. Bus segmentation is recommended for applications using mixed SCSI devices that require high transfer rates.
Bus segmentation can be accomplished using different SCSI cards in the same host or through SCSI cards designed to support multiple busses. As a rule, all Ultra2 SCSI devices should be connected together on the same bus. This will ensure the Ultra2 segment will perform at its optimum level. All slower devices should be connected to a separate SCSI bus.
|
