Chapter 1 Description
Features and Options | Page 1 - 5 |
16-Bit Wide
Synchronous
Transfer
Single-Ended or Differential Signals
the parity drive also significantly increases data availability—the length of time before data is lost due to drive failure.
The controller has SCSI-P connectors (per the SCSI-2 standard) that permit 16- bit wide synchronous data transfers over a single SCSI-P cable on the host interface. The 6500 is a Wide Ultra SCSI device (SCSI-3), transferring data at up to 40 MB/second.
Two methods can be used for sending signals on a SCSI bus— single-endedand differential. Both are functionally equivalent and transparent to the software protocol.
Note Single-ended and differential devices must not be combined on the same SCSI bus. Each 6500 array must be initially ordered as either single-ended (Model 6511) or differential (Model 6512).
•Single-Ended Option
The single-ended option permits the use of a single line for each signal. The line's voltage varies between 0.5 and 3.0 volts DC, with a nominal switching threshold at about 1.4 VDC. Maximum cumulative length of single-ended cabling should not exceed 3.0 meters (approximately 10 feet).
•Differential Option
The differential option consists of two lines designated as a +SIGNAL and a -SIGNAL. A signal is true when the +SIGNAL is more positive than the -SIGNAL, and false when the -SIGNAL is more positive than the +SIGNAL. The differential method is more immune to noise than the single-ended method, and permits the use of much longer cabling— up to 25 meters (approximately 82 feet).
Enclosure | Two horizontal mounting options are available—desktop and rack-mount. (For |
| information on rack-mounting the unit, see documentation included with the |
| optional rack-mount kit.) |
6500 Disk Array User’s Guide | 21020690 B |
