MR0012J 9710 System Assurance Guide 4-13
SCSI Cabling
Cable Length Subtraction
When considering the length of an external SCSI interface bus, you must
subtract the length of bus already inside the 9710 from the maximum allowed
cable length. The individual cable measurements inside the 9710 are:
• From I/O tower to drive: 1.2 m (4 ft)
• Daisy chains between drives: 0.5 m (18 in.) each
• From I/O tower to library control: 2.4 m (8 ft)
• From drive to library control (library control can be daisy chained from the
drive data bus):
- 0.5 m (18 in.), or
- 1.2 m (4 ft), or
-1.8 m (6 ft)
The total length of cable that must be subtracted from each bus is shown in
Table 4-4 . For the IBM AS/400 system, always subtract 1.2 m (4 ft) from the
control or data bus. The AS/400 does not allow daisy chains.
Table 4-4. SCSI Cable Length Subtraction
Number of drives on
the same data bus
Are data and control on
the same bus? (Yes/No)
Subtract this value from
maximum allowed cable length
1 (always 1 for AS/400) no (always no for AS/400) 1.2 m (4.0 ft) from drive bus
2.4 m (8.0 ft) from control bus
2 no 1.7 m (5.5 ft) from drive bus
2.4 m (8.0 ft) from control bus
3 no 2.1 m (7.0 ft) from drive bus
2.4 m (8.0 ft) from control bus
4 no 2.6 m (8.5 ft) from drive bus
2.4 m (8.0 ft) from control bus
5 no 3 m (10.0 ft) from drive bus
2.4 m (8.0 ft) from control bus
6 no 3.5 m (11.5 ft) f rom drive bus
2.4 m (8.0 ft) from control bus
7 no 4 m (13.0 ft) from drive bus
2.4 m (8.0 ft) from control bus
8 no 4.4 m (14.5 ft) f rom drive bus
2.4 m (8.0 ft) from control bus
9 no 5 m (16.0 ft) from drive bus
2.4 m (8.0 ft) from control bus