IBM 8647 - Eserver xSeries 225, Maintenance And Troubleshooting Manual

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An optional external SCSI connector might be installed on the rear of the server.
Use this connector to connect external SCSI devices. The following illustration
shows the SCSI standard 68-pin, female D-shell SCSI connector.
34
1
68
35
Your server has an integrated SCSI controller with RAID capabilities. This
dual-channel controller supports two independent, Ultra320 SCSI channels. The
SCSI connectors for both channels are on the system board. Each channel
supports up to 15 SCSI devices. This controller uses:
v
Double-transition clocking to achieve up to 320 MB-per-second data-transfer
rates
v Domain name validation to negotiate compatible data-transfer speeds with each
device
v
Cyclic-redundancy checking (CRC), instead of the usual parity checking, to
improve data reliability
v An active terminator for SCSI bus termination
Each SCSI device that is connected to a SCSI controller must have a unique SCSI
ID. This ID enables the SCSI controller to identify the device and ensure that
different devices on the same SCSI channel do not attempt to transfer data
simultaneously. SCSI devices that are connected to different SCSI channels can
have duplicate SCSI IDs.
The hot-swap-drive backplane controls the SCSI IDs for the internal hot-swap drive
bays. However, when you attach an external SCSI device to an optional SCSI
adapter, you must set a unique ID for the device. See the information that comes
with the device for instructions to set its SCSI ID.
SCSI cabling requirements
You can install four internal SCSI devices using the SCSI signal cable that comes
with some server models. If you plan to attach external SCSI devices, you must
order an additional SCSI cable, remove the SCSI knockout from the rear of the
server, and connect the new cable from the system board to this opening. To select
and order the correct cables for use with external devices, contact your IBM reseller
or IBM marketing representative. When using an optional SCSI adapter, you must
also connect the SCSI adapter to the SCSI LED (J18) connector on the system
board receive an indication of SCSI hard-disk drive activity. See “System board
internal cable connectors” on page 34 for the location of the SCSI connectors. For
information about the maximum length of SCSI cable, see the American National
Standards Institute (ANSI) SCSI standards on the ANSI Web site at
http://www.ansi.org/ on the World Wide Web. Adhering to these standards will help
to ensure that your server operates properly.
Universal Serial Bus connectors
Use a USB connectors to connect a USB device. USB technology transfers data at
up to 12 megabits per second (Mbps) with a maximum of 127 external devices and
a maximum signal distance of 5 meters (16 ft) per segment. Using Plug and Play
technology, USB devices are configured automatically. The following illustration
shows a USB connector.
Chapter 4. Installing options
77