The Scsi Bus And This Drive; Mixing Wide And Narrow Devices - HP 220mx User Manual

Operating This Drive on a SCSI Bus

The SCSI Bus and This Drive

The SCSI Bus and This Drive
This drive is a "fast and narrow" SCSI device that uses a single-ended SCSI bus.
When deciding on whether to have multiple devices on the same SCSI bus, you
should consider the following:
• How are the devices going to be used? What performance is expected from each
device?
• If the decision is made to have multiple devices on the same bus, what SCSI
requirements must be observed to make sure the bus will work?
Consider the quantity of data that the bus will have to carry, the frequency of data
transfer, and the priority of this data transfer in your business. If you expect to be
using the drive in the same time-frame as another device, or devices, you may
experience a drop in performance.

Mixing Wide and Narrow Devices

An a preliminary note to this discussion, HP highly recommends that you do NOT
mix wide and narrow buses.
Connecting devices of the same bus width, such as all narrow (50-pin) is a simple
process of daisy-chaining the devices, and terminating both ends of the bus.
However, mixing narrow and wide devices invites problems.
This method should only be implemented by an experienced systems integrator who
is highly knowledgeable about SCSI. Since the wide (68-pin) buses need more data
lines on the bus for their data transfer, it's necessary that the cables connecting the
devices are 68 pin. The data would be lost if the devices were set up as depicted in
the figure below.
B-6 Appendix B