IBM 865741Y Handbook - Page 92

SCSI Drives Some drives have a special design called small computer system interface (SCSI). This design allows you to attach multiple drives to a single connector. Note: Any information about SCSI drives also applies to other SCSI devices, such as scanners and printers. Your 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 your server supports, go to http://www.us.pc.ibm.com/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 your 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 your server. (See "Using the SCSISelect Utility" on page 46 for more information.) 74 Netfinity 3500 User's Handbook