Dell PowerVault TL4000 Dell Model TL2000/TL4000 Tape Library- User's Guide - Page 52

Using Multiple SCSI Buses, Type of Interconnection, Maximum Bus Length Between Terminators in, meters

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v The SCSI bus is terminated properly at each end v Cable restrictions are followed according to the SCSI-3 specification Under the SCSI-3 protocol, this type of attachment allows cable lengths of up to 25 m (81 ft) with the appropriate cable and terminator. The table below gives the maximum bus length between terminators for the LVD interface. Table 3-2. Maximum bus length between terminators Type of Interconnection Maximum Bus Length Between Terminators (in meters) Point-to-point (1 server and 1 drive) 25 Multi-drop/daisy-chain (1 server and multiple 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 "Using Multiple SCSI Buses"), and Ultrium Tape Drives must be the only target devices that are active on the bus. Note: Daisy-chaining is NOT recommended due to potential issues with SCSI bus performance, SCSI cables/connectors, and host bus adapters. Note: For maximum performance, the quantity of tape drives that you can attach to one SCSI bus is limited, and is based on the type of bus that you have and the amount of data compression achieved. Ultra160 SCSI buses have a bandwidth of 160 MB per second. The table below lists the types of SCSI buses and gives the recommended maximum quantity of drives that you can attach. Table 3-3. Recommended maximum quantity of drives per SCSI bus Type of Drive Ultra 160 SCSI Bus LVD Ultrium 3 1 drive at 2:1 compression Using Multiple SCSI Buses The library has two SCSI connectors for each tape drive in the library. Each drive can be daisy-chained using a SCSI bus jumper. Note: Daisy-chaining is NOT recommended due to potential issues with SCSI bus performance, SCSI cables/connectors, and host bus adapters. Removal of any jumpers will create a SCSI bus for each drive installed in your library for attachment to multiple servers or to multiple SCSI adapter cards on one server. Remember that each SCSI bus must be terminated. Multiple SCSI buses may be required for maximum performance, depending on the application and data compression ratio. Note, however, that library (Medium Changer) control is required on at least one SCSI bus. The Medium Changer device is required to be addressed via LUN 1 of the lowest-numbered drive position of each logical library. The Medium Changer device may additionally be addressed via LUN 1 of other drives in any logical library. 3-8 Dell PowerVault TL2000 Tape Library and TL4000 Tape Library User's Guide

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v
The SCSI bus is terminated properly at each end
v
Cable restrictions are followed according to the SCSI-3 specification
Under the SCSI-3 protocol, this type of attachment allows cable lengths of up to 25
m (81 ft) with the appropriate cable and terminator. The table below gives the
maximum bus length between terminators for the LVD interface.
Table 3-2. Maximum bus length between terminators
Type of Interconnection
Maximum Bus Length Between Terminators (in
meters)
Point-to-point (1 server and 1 drive)
25
Multi-drop/daisy-chain (1 server and
multiple 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 “Using
Multiple SCSI Buses”), and Ultrium Tape Drives must be the only target devices
that are active on the bus.
Note:
Daisy-chaining is NOT recommended due to potential issues with SCSI bus
performance, SCSI cables/connectors, and host bus adapters.
Note:
For maximum performance, the quantity of tape drives that you can attach
to one SCSI bus is limited, and is based on the type of bus that you have
and the amount of data compression achieved. Ultra160 SCSI buses have a
bandwidth of 160 MB per second. The table below lists the types of SCSI
buses and gives the recommended maximum quantity of drives that you can
attach.
Table 3-3. Recommended maximum quantity of drives per SCSI bus
Type of Drive
Ultra 160 SCSI Bus
LVD Ultrium 3
1 drive at 2:1 compression
Using Multiple SCSI Buses
The library has two SCSI connectors for each tape drive in the library. Each drive
can be daisy-chained using a SCSI bus jumper.
Note:
Daisy-chaining is NOT recommended due to potential issues with SCSI bus
performance, SCSI cables/connectors, and host bus adapters.
Removal of any jumpers will create a SCSI bus for each drive installed in your
library for attachment to multiple servers or to multiple SCSI adapter cards on one
server. Remember that each SCSI bus must be terminated. Multiple SCSI buses
may be required for maximum performance, depending on the application and
data compression ratio. Note, however, that library (Medium Changer) control is
required on at least one SCSI bus.
The Medium Changer device is required to be addressed via LUN 1 of the
lowest-numbered drive position of each logical library. The Medium Changer
device may additionally be addressed via LUN 1 of other drives in any logical
library.
3-8
Dell PowerVault TL2000 Tape Library and TL4000 Tape Library User's Guide