HP Surestore Disk Array 12h - And FC60, Advanced User'S Manual, Page: 178 / 466

178
Configuration Switches
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).
Note
In full bus mode, all ten disks can be accessed through either BCC. However,
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
Table 25 ). The two ID ranges include
Table 24
Disk Enclosure Switches
Switch
Setting
Operation
1 - Full-/Split Bus Mode
1 Full-Bus Mode
0 Split-Bus Mode
2 - Stand-Alone/Array Mode 0 Always set to Off (Array Mode)
3 - Bus Reset on Power Fail 0 Must be set to 0
4 - High/Low Bus Addressing 0 Set to 0 (Low addressing)
5 - Not Used 0 Not used; must be set to 0