Disk Numbers

Disk Numbers

A disk number is assigned to a disk drive, or to an array, when the SSA configurator attaches that disk drive, or array, to the system. (That is, the disk drive, or array, becomes a system resource.)

The number that is assigned is related to the position in the System Resource List at which the resource (disk drive or array) is attached.
The SSA configurator provides an option that allows the user to change the disk number to another number, if required. Valid numbers are 1 through 255.

Disk numbers are similar to the SCSI ID settings on SCSI disk drives. The system software uses the disk numbers to map the disk drives to a logical bus, target, and LUN.
The logical bus number to which a system resource is mapped is:

Disk number divided by 32

where 32 is the number of targets on each bus. Therefore, a disk number that is lower than 32 is mapped to logical bus 0.

The target address is the remainder that results from dividing the disk number by 32.

      For example:
      Disk Number       Mapping
          2             Logical Bus 0 Target 2
         32             Logical Bus 1 Target 0
         37             Logical Bus 1 Target 5
         65             Logical Bus 2 Target 1

The device is always mapped to LUN 0.
Microsoft Cluster Server requires that the boot device be on a different logical bus from any shared disks.

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