In addition to the features supported with the IBM SCSI-2 F/W PCI Adapter, the IBM SCSI-2 F/W RAID adapter provides a RAID controller. Please reference 1.6.5, ªRAID Technologyº on page 22for a discussion on RAID.

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

SCSI-2

SCSI-2

 

with no Cache

SCSI Adapter

Fast/Wide

Fast/Wide

 

 

with Cache

Adapter/A

Streaming

 

 

 

 

RAID

 

 

 

 

Adapter/A

 

 

 

 

 

SCSI Bus Width

16-bit

32-bit

32-bit

32-bit

 

 

 

 

 

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 SCSI-II.

The 720 will support 80 MBps data streaming with the SCSI-2 Fast/Wide Streaming RAID Adapter/A N/A = not available

Table 4. PCI SCSI Adapters Summary

Attribute

PCI SCSI-2 Fast

PCI SCSI-2

PCI SCSI-2

 

Adapter

Fast/Wide Adapter

Fast/Wide RAID

 

 

 

Adapter

 

 

 

 

SCSI Bus Width

32-bit

32-bit

32-bit

 

 

 

 

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 SCSI-II

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 On-board cache size

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

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IBM SG24-4576-00 manual Hard Disk Drives, Summary