Setting the SCSI identifier value

Last published : Jun 11, 2026
SCSI adapters are typically set with a default identifier value of 7. Each device on a SCSI bus must have a unique SCSI identifier value. When more than one system is connected to a SCSI bus, you must change the SCSI identifier to a unique number. You must make this change to one or more systems, usually the unique number is 5 or 6.
Perform the procedure if you want to connect to shared storage with shared SCSI devices.
Figure: Cabling the shared storage
Cabling the shared storage
To set the SCSI identifier value
  1. Determine the SCSI adapters on each system:
    north # lsdev -C -c adapter | grep scsi
    scsi0   Available 11-08    Wide/Ultra-2 SCSI I/O Controller
    scsi1   Available 11-09    Wide/Ultra-2 SCSI I/O Controller
    south # lsdev -C -c adapter | grep scsi
    scsi0   Available 11-08    Wide/Ultra-2 SCSI I/O Controller
    scsi1   Available 11-09    Wide/Ultra-2 SCSI I/O Controller
    1. Verify the SCSI ID of each adapter:
    north # lsattr -E -l scsi0 -a id
    id 7 Adapter card SCSI ID True
    north # lsattr -E -l scsi1 -a id
    id 7 Adapter card SCSI ID True
    south # lsattr -E -l scsi0 -a id
    id 7 Adapter card SCSI ID True
    south # lsattr -E -l scsi1 -a id
    id 7 Adapter card SCSI ID True
  2. If necessary, change the SCSI identifier on each system so that it is unique:
south # chdev -P -l scsi0 -a id=5
scsi0 changed
south # chdev -P -l scsi1 -a id=5
scsi1 changed
  1. Shut down all systems in the cluster.
  2. Cable the shared storage as illustrated in Figure: Cabling the shared storage.
  3. Restart each system. After all systems have booted, use the lspv command to verify that each system can see all shared devices needed by the application.
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