IBM 84875MU, Руководство пользователя

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Serial connectors
Use the serial connectors to connect serial devices. The following illustration shows
a serial connector.
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Ultra320 SCSI connector
You can install up to four internal SCSI devices using the SCSI cable that comes
with some models of the server. Other server models might come with one SCSI
cable that is connected from the internal SCSI connector to the standard
hot-swap-drive backplane. You can attach additional internal SCSI devices to the
other internal SCSI connector, or you can use the connector to attach external SCSI
devices. To connect external SCSI devices, remove the SCSI knockout from the
rear of the server and secure the free end of an optional cable in the new opening.
If you want to attach external SCSI devices to the server without using the internal
SCSI channel, you must install an optional SCSI adapter.
Notes:
1. External SCSI devices connected to internal SCSI channels will operate
asynchronously.
2. If you install a PCI RAID adapter to configure and manage the internal hot-swap
drives, you must move the SCSI cable from the system-board SCSI connector
to an internal channel connector on the RAID adapter (see “Cabling an optional
SCSI adapter” on page 46).
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.
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68
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The server has an integrated SCSI controller with RAID capabilities that supports
up to 15 SCSI devices. The SCSI connector for the control is on the system board.
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.
Chapter 5. Input/output connectors
55