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IBM-AUSTRIA - PC-HW-Support 30 Aug 1999 |
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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