v Domain-name validation to negotiate compatible data-transfer speeds with eachdevicev Cyclic redundancy checking (CRC), instead of the usual parity checking, toimprove data reliabilityv An active terminator for SCSI bus terminationThe server comes with one SCSI cable, which connects the internal connector onthe system board to the standard hot-swap-drive backplane. If you plan to attachexternal SCSI devices, you must order additional cables. To select and order thecorrect cables for use with external devices, contact your IBM marketingrepresentative or authorized reseller.SCSI cabling requirementsFor information about the maximum length of SCSI cable, go to the AmericanNational Standards Institute (ANSI) SCSI standards on the ANSI Web site athttp://www.ansi.org/. Adhering to these standards will help to ensure that the serveroperates properly.SCSI IDsEach SCSI device that is connected to a SCSI controller must have a unique SCSIID. This ID enables the SCSI controller to identify the device and ensure thatdifferent devices on the same SCSI channel do not attempt to transfer datasimultaneously. SCSI devices that are connected to different SCSI channels canhave duplicate SCSI IDs. Table 5 lists the SCSI IDs for the hard disk drives andbackplanes that are connected to one channel.Table 5. SCSI IDs for standard hot-swap hard disk drives, controller, and backplaneDevice SCSI IDDrive bay 1 0Drive bay 2 1Drive bay 3 2Drive bay 4 3Drive bay 5 4Drive bay 6 5Controller 7Backplane 8The hot-swap-drive backplane controls the SCSI IDs for the internal hot-swap drivebays. However, when you attach an external SCSI device to an optional SCSIadapter, you must set a unique ID for the device. See the information that comeswith the device for instructions for setting its SCSI ID.SCSI connectorThe following illustration shows a SCSI connector.34 168 35Chapter 3. Installing options 45
