v The SCSI bus is terminated properly at each endv Cable restrictions are followed according to the SCSI-3 specificationUnder the SCSI-3 protocol, this type of attachment allows cable lengths of up to 25m (81 ft) with the appropriate cable and terminator. The table below gives themaximum bus length between terminators for the LVD interface.Table 3-2. Maximum bus length between terminatorsType of InterconnectionMaximum Bus Length Between Terminators (inmeters)Point-to-point (1 server and 1 drive) 25Multi-drop/daisy-chain (1 server andmultiple drives) 12 (LVD)Note: The maximum bus lengths stated in this table include the internal length of the bus.For maximum performance, multiple SCSI buses may be required (see “UsingMultiple SCSI Buses”), and Ultrium Tape Drives must be the only target devicesthat are active on the bus.Note: Daisy-chaining is NOT recommended due to potential issues with SCSI busperformance, SCSI cables/connectors, and host bus adapters.Note: For maximum performance, the quantity of tape drives that you can attachto one SCSI bus is limited, and is based on the type of bus that you haveand the amount of data compression achieved. Ultra160 SCSI buses have abandwidth of 160 MB per second. The table below lists the types of SCSIbuses and gives the recommended maximum quantity of drives that you canattach.Table 3-3. Recommended maximum quantity of drives per SCSI busType of Drive Ultra 160 SCSI BusLVD Ultrium 3 1 drive at 2:1 compressionUsing Multiple SCSI BusesThe library has two SCSI connectors for each tape drive in the library. Each drivecan be daisy-chained using a SCSI bus jumper.Note: Daisy-chaining is NOT recommended due to potential issues with SCSI busperformance, SCSI cables/connectors, and host bus adapters.Removal of any jumpers will create a SCSI bus for each drive installed in yourlibrary for attachment to multiple servers or to multiple SCSI adapter cards on oneserver. Remember that each SCSI bus must be terminated. Multiple SCSI busesmay be required for maximum performance, depending on the application anddata compression ratio. Note, however, that library (Medium Changer) control isrequired on at least one SCSI bus.The Medium Changer device is required to be addressed via LUN 1 of thelowest-numbered drive position of each logical library. The Medium Changerdevice may additionally be addressed via LUN 1 of other drives in any logicallibrary.3-8 Dell PowerVault TL2000 Tape Library and TL4000 Tape Library User's Guide
