The numbering scheme

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The following library elements are numbered:

  • Modules
  • Slots (storage and I/O)
  • Drives

The library controller cards and power supplies are not numbered separately. They are identified according to the module in which they are installed.

Logical Element IDs

Logical Element IDs are the primary method that is used in library interfaces and logs to uniquely identify each library element for status and fault messages. They are called “logical IDs” or just “IDs”. All elements are numbered, starting at 1, from the lowest on up. A 21U Library can have up to 7 modules. A 48U Library can have up to 16 modules. Only installed drives are assigned a drive ID. Slots in the magazines are sequentially numbered from front to back. The numbering begins with the left-side magazine, at the lowest slot, and progresses to the top front slot of the right-side magazine. Slot IDs have the number of the module listed first, then a dot (.) and then the slot ID within the module. For example, 2.5 would be the 5th slot in module 2.

See the example for a 3 module 21U library. Element IDs are handled the same for a 48U Library.

Physical Element Numbering

Sometimes an element ID has a different number (often in parentheses) next to it. This number is called a Physical Number, Phy Num, or PNUM. PNUMs are used by the software and are only useful in complex troubleshooting. They are referenced to the base module, so they do not change when modules are added or removed from the library. For example, 2 (4) would be the designation for the base module in the library example above. The module ID is 2 and it has a PNUM of 4. Configuring logical libraries does not change the element ID or PNUM, it just assigns the element to a specific logical library.

SCSI Element Addressing

SCSI Element Addressing (defined by industry SCSI standards) assigns identifiers to library elements that are used by software applications. SCSI element addresses appear in logs and library interfaces along with Element IDs and PNUMs. Configuring logical libraries changes the SCSI element addresses.

Appendix XXXX gives a more detailed description of numbering systems along with more examples.