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Parts Information

Document ID: DDSE-44JGJK

Netfinity 3500 - SCSI Drives

Applicable to: World-Wide

SCSI Drives

Note Any information about SCSI drives also applies to other SCSI devices, such as scanners and printers.

The Netfinity 3500 server supports drives that comply with American National Standards Institute (ANSI) SCSI Standards X3.131-1986 (SCSI), X3.131-1994, (SCSI-2), X3.277-1996 (SCSI-3 Fast-20 parallel interface), and X3.253-1995 (SCSI-3 parallel interface).

For a complete list of the SCSI devices that the server supports, go to http://www.pc.ibm.com/us/server/ on the World Wide Web.

SCSI Physical Unit Numbers: When more than one physical device is connected to the same UltraSCSI controller, the devices compete for support from the UltraSCSI controller. Because the UltraSCSI controller communicates with only one device at a time, the priority of a device is based on its SCSI identification (ID). The highest priority IDs are 7 to 0; the lowest priority IDs are 15 to 8.

If you install additional SCSI devices, you must set a unique ID for each SCSI device that you connect to the integrated SCSI-2 connector. This unique ID enables the UltraSCSI controller to identify the devices and to prevent two devices from sending or receiving data on the SCSI bus at the same time. SCSI devices use a variety of methods to set the SCSI ID, such as jumpers, thumbwheels, or switches.

The SCSI device ID is also known as the SCSI address or physical unit number (PUN).

The UltraSCSI controller in the server supports SCSI IDs 0 to 15; ID 7 is reserved for the controller. The default startup (boot) SCSI ID is 0 for an internal SCSI hard disk drive in Channel A. Use SCSISelect to view the SCSI IDs of SCSI devices in the server. (See "SCSISelect Utility" on page 42 for more information.)

If you install wide (16-bit) SCSI devices, you can set the IDs to any whole number between 0 and 6, or between 8 and 15. If you install narrow (8-bit) SCSI devices, you can set the IDs to any whole number between 0 and 6.

SCSI Logical Unit Number: Each physical device has a physical unit number (PUN) and a logical unit number (LUN). If a physical device supports no logical devices, its LUN is 0. Most SCSI devices support only LUN 0. Certain types of physical SCSI devices ( bridge controllers) can support more than one logical device.

For example, a printer controller might support up to eight printers. The printer controller is a physical device, and each printer is a logical device. If the printer controller is assigned to ID 2, the ID of the first printer appears in the SCSI device configuration as PUN 2, LUN 0. The IDs of the other printers are PUN 2, LUN 1; PUN 2, LUN 2; on up to PUN 2, LUN 7.

Termination Requirements: All Netfinity 3500 servers come with an UltraSCSI controller on the system board. This UltraSCSI controller provides termination for one end of the SCSI bus and the cable provides termination for the the end of the SCSI bus. Any SCSI devices that are installed must have their termination set to Disabled.

When you install devices in bays 2, 3, 5, and 6, you must disable the termination for the devices before you install them.

If you connected external SCSI devices to the server, set the termination for the last device on the external cable to Enabled. See the device documentation for instructions.

Refer to the instructions that come with the SCSI device for more information about termination.

	Search Keywords
	Document Category	Hard Drives, Optical Drives, Printers, Tape Drives
	Date Created	27-01-99
	Last Updated	27-01-99
	Revision Date	27-01-2000
	Brand	IBM PC Server
	Product Family	Netfinity 3500
	Machine Type	8644
	Model
	TypeModel
	Retain Tip (if applicable)
	Reverse Doclinks and Admin Purposes