HP Surestore Disk Array 12h - And FC60 Service Manual page 144

Table 18
Disk Enclosure Switches
Switch
1 - Full-/Split Bus Mode
2 - Stand-Alone/Array Mode
3 - Bus Reset on Power Fail
4 - High/Low Bus Addressing
5 - Not Used
Full-Bus/Split-Bus (Switch 1) Configuration
The disk enclosure's internal bus connects the disk drives together and to the BCCs. This
bus can be set for two modes of operation: full-bus or split-bus mode. When switch 1 is set
to Full Bus (1), all ten disk can be accessed together on a single SCSI bus. In this mode, one
SCSI channel from the FC60 controller is connected to all ten disk modules through either
BCC (typically BCC A).
In full bus mode, all ten disks can be accessed through either BCC. However,
Note
internally each BCC still manages five disks. This means that if the BCC that is
not connected to a SCSI channel fails, access to its five disks will be lost. Failure
of the BCC that is connected to a SCSI channel will render all ten disks
inaccessible.
When switch 1 is set to 0 (split-bus mode), the disk enclosure is split into two separate
buses with five disks to each bus. In split-bus mode, each bus is controlled by a separate
BCC. BCC A (the top BCC) controls the even drive slots (0, 2, 4, 6, 8) and BCC B (the
bottom BCC) controls the odd bus slots (1, 3, 5, 7, 9). In split-bus mode, two SCSI channels
are connected to the disk enclosure, one to a SCSI connector on BCC A and a second a
SCSI connector on BCC B.
Each slot in the disk enclosure is assigned a SCSI ID. A range of IDs is assigned to the odd
disk slots, and a different range to the even slots (see
Configuration Switches
144
Setting
Operation
1 Full-Bus Mode
0 Split-Bus Mode
0 Always set to Off (Array Mode)
0 Must be set to 0
0 Set to 0 (Low addressing)
0 Not used; must be set to 0
Table 19). The two ID ranges include