IBM 3531 manual Unit ID dial switch

Attention: A loss of data can occur if you change the position of internal option switch 1 or internal option switch 3 after storing data on the drives. Refer to “Conversion of EXP300 to a tower or from a tower” on page 25 if you want to change the configuration of your expansion unit from a rack (internal switch 1 Off) to a tower (internal switch 1 On) or from a tower to a rack orientation.

SCSI buses and IDs

There are two SCSI buses (bus 1 and bus 2) in the expansion unit. Each bus uses seven SCSI ID numbers. Each disk drive within the expansion unit has a unique SCSI bus and ID assignment, based on its physical location in the expansion unit and the setting of option switch 1 (inside the switch card).

Option switch 1 — SCSI-address switch

This switch sets the order of the SCSI IDs. The default is Off for a rack unit installation. In the rack unit, the SCSI IDs are from left to right, 0, 1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, and 14. When this switch is set to On for a tower installation, the SCSI IDs are from top to bottom, 0, 1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, and 14.

Option switch 2 — Rack/tower LED switch

Note: If you are installing the EXP300 in a tower, refer to the Rack-to-Tower Conversion Kit instructions for option switch settings and labeling information.

Option switch 2 is the rack and tower mode switch. Put this switch in the Off position when the unit is placed in a rack and in the On position when the unit is placed in a tower.

When shipped, option switch 2 is set to the rack (Off) position. When you make the change to install it into a tower, option switch 2 is in the On position and the general system error indicator on the front panel is swapped with the power-on LED, placing the green power-on LED above the general-system error indicator.

Set this switch to Off (the default) for a rack unit and On for a tower unit.

Option switch 3 — SCSI bus split switch

This switch controls the SCSI bus configuration. When this option switch is set to Off (the default), the expansion unit configuration is set as a single SCSI bus mode. When this option switch is set to On, the expansion unit configuration is set as a dual SCSI bus (split bus) mode.

Option switch 4 — Reserved

This switch is reserved; leave this option switch set to Off (the default).

Unit ID dial switch

The unit ID switch has 10 settings. You can use these settings (0 through 9) to set an ID for the expansion unit. System-management software, such as IBM Netfinity Director, uses this expansion unit ID when it provides data and alerts for the expansion unit.

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