Card Assembly Switches - IBM 2104 Model DS4 Installation Manual

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Figure 38. Card assembly switches
10. The SCSI bus split control 7 controls the SCSI bus mode. When the switch
11. Verify that switch 8 and 9 (reserved) are off.
12. Verify that the disable ID 6 handling switch 10 is off. The SCSI ID 6 is
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Expandable Storage Plus 2104 Model DS4 Installation Guide
9. Figure 38 shows other switches on the SCSI interface card.
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is off, the enclosure is configured as a single SCSI bus. When this switch is
on, the enclosure is configured as a dual or split SCSI bus.
automatically disabled and removed from the system when the following
conditions are met:
v The switch is off.
v Two SCSI interface cards are installed with single-bus configuration.
v Two hosts are connected to the 2104 Model DS4 and both are on.
When you install two SCSI Interface cards and you configure the 2104 Model
DS4 for single-bus mode, an ID conflict occurs if you install a drive in the slot
of SCSI ID 6. The ID conflict exists because one of the host bus adapter
(HBA) SCSI IDs should be set to 6 when using both host ports. Unless the
disable ID 6 handling switch is off or the drive is removed from the slot of
SCSI ID 6, there will be an ID conflict between the HBA that is using ID 6 and
the drive in the slot of SCSI ID 6. Removing the drive from slot 6 and replacing
it with a dummy carrier eliminates the conflict.
An alternative is to turn the disable ID 6 handling switch off, which
continuously applies a SCSI RESET signal to the drive in the slot of ID 6 when
TERMPWR is present on both JBOD interface cards. While the drive is held in
RESET, it releases all bus signals, effectively removing it from the system. The
drive in the slot of SCSI ID 6 will continuously remain in RESET under these
conditions until power is removed and the disable SCSI ID 6 handling switch is
on.
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