Recommended Maximum Quantity Of Drives - IBM System Storage TS3310 Setup And Operator Manual

Table 2-5. Maximum bus length between terminators
Type of Interconnection
Point-to-point (1 server and 1 drive)
Multi-drop/daisy-chain (1 server and
multiple drives)
For maximum performance, multiple SCSI buses may be required (see "Using
Multiple SCSI Buses"), and IBM Ultrium Tape Drives must be the only target
devices that are active on the bus.
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; Ultra320 SCSI buses have a bandwidth of
320 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 2-6. Recommended maximum quantity of drives per SCSI bus
Type of Drive
LVD Ultrium 3
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 that is included with each tape
drive.
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. 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.
Any bus containing a Medium Changer device via LUN 1 of a drive is referred to
as a control and data path. Any other bus is referred to as a data path. For
information about control paths, see "Using Multiple Control Paths" on page 2-2.
Terminating the Bus
The SCSI bus and all of the wires in the SCSI cable must be properly terminated
according to the SCSI standard.
You can plug an external terminator into one of the SCSI connectors. A terminator
must be installed on the last device on each end of a string of multiple devices. A
terminator is included with each Ultrium Tape Drive.
Maximum Bus Length Between
Type of SCSI Bus
Ultra160
2 (1 drive at 2:1 compression) 2 (1 drive at 2:1 compression)
Terminators (in meters)
25
12 (LVD)
Ultra320
Chapter 2. Installation Planning
2-9