
In addition to the features supported with the IBM
1.6.3.1 Summary
The following tables summarize the features of the IBM SCSI adapters.
Table 3. SCSI Adapters Summary
Attribute | SCSI Adapter | Enhanced | ||
| with no Cache | SCSI Adapter | Fast/Wide | Fast/Wide |
|
| with Cache | Adapter/A | Streaming |
|
|
|
| RAID |
|
|
|
| Adapter/A |
|
|
|
|
|
SCSI Bus Width | ||||
|
|
|
|
|
SCSI Data Transfer Rate | 5 MBps | 5 MBps | 20 MBps | 20 MBps |
|
|
|
|
|
Micro Channel Data Transfer Rate | 8.3 MBps | 16.6 MBps | 20 MBps | 40/80 MBps |
|
|
|
|
|
Parity | Optional | Optional | Yes | Yes |
|
|
|
|
|
Tagged Command Queueing | N/A | N/A | Yes | Yes |
(TCQ) |
|
|
|
|
|
|
|
|
|
Systems where implemented |
|
| 500 | 500/720 |
|
|
|
|
|
Note: Fast and Wide are data transfer methods as defined in
The 720 will support 80 MBps data streaming with the
Table 4. PCI SCSI Adapters Summary
Attribute | PCI | PCI | PCI |
| Adapter | Fast/Wide Adapter | Fast/Wide RAID |
|
|
| Adapter |
|
|
|
|
SCSI Bus Width | |||
|
|
|
|
SCSI Data Transfer Rate | 10 MBps | 20 MBps | 20 MBps |
|
|
|
|
Parity | Yes | Yes | Yes |
|
|
|
|
Tagged Command Queueing (TCQ) | Yes | Yes | Yes |
|
|
|
|
Systems where implemented | PC Server 300/310 | PC Server 320/520 | PC Server 320/520 |
|
|
|
|
Note: Fast and Wide are data transfer methods as defined in
1.6.4 Hard Disk Drives
Ultimately, the hard disk drive is the component that has the most effect on subsystem performance. The following specs should be considered when evaluating hard disks in order to optimize performance:
∙
∙
∙
Average access time Maximum transfer rate
Average access time is one of the standard indicators of hard drive performance. This is the amount of time required for the drive to deliver data after the computer sends a read request. It is composed of two factors, the seek time and the rotational delay. The seek time is the time necessary to position the heads
Chapter 1. IBM PC Server Technologies 21