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To configure the Storage Array, complete the following actions:
1. Cable the host system(s) to the Storage Array.
2. Set the bus join switch on the Storage Array(s) as appropriate.
This chapter details the configuration actions within the following sections:
The Storage Array front chassis supports nine modules: one I/O module, up to six SCSI hard disk drives equipped with 80-pin SCA-2 connectors, and up to two AC or two DC power supplies. The backplane can be configured as a single bus supporting up to six disk drives (join mode) or as two buses supporting up to three drives each (split-bus mode). Join or split-bus mode is determined by the position of the bus join switch and the I/O module cabling connections, as described in Table 4-1.
| SCSI 0 Connector | SCSI 1 Connector | Bus Join Switch | SCSI IDs for Drives and VEM | Comments |
|---|---|---|---|---|
| Primary array configurations | ||||
Host cable | Empty | To left (off) | 8, 9, 10, 11, 12, 13, | Single bus, join mode |
Empty | Host cable | To left (off) | 8, 9, 10, 11, 12, 13, | Single bus, join mode |
Host 1 cable | Host 2 cable | To left (off) | Host 1 IDs = 8, 9, 10, Host 2 IDs =11, 12, 13 | Split-bus mode with two hosts |
Empty | Cable from expansion array | To left (off) | 8, 9, 10, 11, 12, 13, | Single bus, join mode |
Cable from expansion array | Empty | To left (off) | 8, 9, 10, 11, 12, 13, | Single bus, join mode |
| Expansion array configurations | ||||
Host cable | Cable to primary array | To right (on) | 1, 2, 3, 4, 5, 6, VEM = 14 | Single bus, join mode |
Cable to primary array | Host cable | To right (on) | 1, 2, 3, 4, 5, 6, VEM = 14 | Single bus, join mode |
The I/O module, inserted in the far left slot, has two VHDCI connectors labeled SCSI 1 and SCSI 0 (see Figure 4-1) to accommodate SCSI cables that connect to host systems or to another Storage Array. When configured in split-bus mode, the SCSI 1 connector interfaces with SCSI bus 1, and the SCSI 0 connector interfaces with SCSI bus 0. In join mode, either connector can interface with all installed disk drives. When only one cable is attached to the I/O module, the Storage Array is forced into join mode regardless of the bus join switch setting.
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Caution Make sure to tighten the jack screws on the SCSI cable. A loose cable connection can cause data corruption. |
The bus join switch is located on the back panel of the Storage Array, as shown in Figure 4-2. A tool, such as a small screwdriver, is required to change the setting of the switch. When set to the right, join mode is on. When set to the left, join mode is off. Table 4-1 summarizes the supported Storage Array and bus join switch combinations.
No external terminators are required. If the Storage Array detects that no cable is attached to an I/O module connector, it automatically terminates the SCSI bus at the open connector.
A Storage Array can be installed either as a primary array or as an expansion array. In either case, unique SCSI IDs are assigned automatically for the VEM and for each disk drive in the Storage Array.
The Storage Array connected at the end of the SCSI daisy chain is the primary array. An expansion array is a Storage Array that is cabled between the host and the primary array. Table 4-2 summarizes the SCSI ID assignments for a primary and an expansion array as well as the associated VEMs.
| Primary Array | Expansion Array | |
|---|---|---|
VEM SCSI ID | 15 | 14 |
Disk drive SCSI IDs | 8, 9, 10, 11, 12, 13 | 1, 2, 3, 4, 5, 6 |
Three basic configurations of the Storage Array are supported.
Figure 4-3 depicts a single host system connected to a single Storage Array.
Explanation
The host can be connected to either SCSI 0 or SCSI 1 on the I/O module. When only one cable is connected to the I/O module, the Storage Array joins SCSI bus 0 and SCSI bus 1, and terminates the joined bus at the empty connector. The disk drives receive the SCSI IDs 8, 9, 10, 11, 12, and 13. The VEM SCSI ID is 15.
In this case, the setting of the bus join switch is irrelevant.
Figure 4-4 depicts two host systems connected to a Storage Array in a split-bus configuration.
Explanation
When host cables are connected to both I/O module connectors, the Storage Array splits the backplane into SCSI bus 0 (accessed by the SCSI 1 connector) and SCSI bus 1 (accessed by the SCSI 0 connector). The host connected to SCSI 0 accesses the hard drives with SCSI IDs 8, 9, and 10. The host connected to SCSI 1 accesses drives with SCSI IDs 11, 12, and 13. The VEM is assigned SCSI ID 15.
The bus join switch is set to the left (off). If the switch were set to the right (on), the Storage Array unit would become an expansion array with a single bus.
Figure 4-5 depicts a single host system connected with two daisy-chained Storage Arrays.
Explanation
The host cable and expansion cable can be connected to either SCSI 1 or SCSI 0. The bus join switch on the unit attached to the host is set to the right (on) to force-join SCSI bus 0 and SCSI bus 1. The host has access to all six disks on that unit. The switch on the other unit is set to the left (off), but the buses are joined because one connector is open. The Storage Array terminates the SCSI bus at the open connection. The terminated Storage Array is the primary array with hard drive SCSI IDs of 8, 9, 10, 11, 12, and 13. The VEM SCSI ID is 15. The unit between the host and the primary array is the expansion array, with hard drive expansion SCSI IDs of 1, 2, 3, 4, 5, and 6. The VEM SCSI ID is 14.
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Note An expansion array must be physically placed on the SCSI bus between the host system and the primary array to preserve the SCSI ID assignments of the primary array. |
Posted: Mon Aug 28 18:03:45 PDT 2000
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