IBM DS4700 manual Enclosure ID of storage expansion enclosures in a, Redundant drive channel

If required, use a small screwdriver or the tip of a pen to push the small buttons above and below each enclosure ID digit to change the enclosure ID setting. Press the button located above the digit to lower the digit by one. Press the button located below the digit to raise the digit by one.

Note: Some DS4000 storage expansion enclosures ship with a panel installed over the enclosure ID switch to prevent the enclosure ID from being changed accidentally. If your DS4000 storage expansion enclosure has a protective panel over the ID switch, use a pencil or a small screwdriver to change the enclosure ID.

Each storage expansion enclosure in a DS4000 Storage Subsystem drive loop must have a unique enclosure ID. DS4000 controllers use a combination of the enclosure ID and the number of the physical slot that a hard drive occupies to create a unique fibre channel loop address or arbitrated loop physical address (AL_PA) for each drive in a fibre channel drive loop. The enclosure ID consists of two digits, a tens digit (x10) and ones digit (x1).

Attention: When connecting storage expansion enclosures, you must use the tens digit (x10) enclosure ID setting to distinguish different redundant drive channel pairs and use the ones digit (x1) enclosure ID setting to distinguish storage expansion enclosures IDs within a redundant drive channel pair. For example, in a DS4700 Express configuration with six EXP710 or EXP100 storage expansion enclosures connected in a redundant drive channel/loop pair, the recommended enclosure ID settings for the enclosures are shown in Table 30. EXP810 storage expansion enclosures automatically set their enclosure IDs to be unique in a drive channel pair.

Table 30. Recommended enclosure ID settings scheme when connecting a DS4700 to EXP710s or EXP100s

	Enclosure ID of storage expansion enclosures in a
	redundant drive channel
Enclosure 1	11
Enclosure 2	12
Enclosure 3	13
Enclosure 4	14
Enclosure 5	15
Enclosure 6	16

The DS4700 Express normally ships with an enclosure ID outside the range of 00–77. However, if your DS4700 Express enclosure ID was set to a value within the range of 00–77, it may be in conflict with the enclosure ID of one of the drive expansion enclosures that you are trying to attach to the DS4700 Express. If this is the case, the amber ID Conflict LED on the storage expansion enclosure will light after you power on the storage subsystem.

Give each storage expansion enclosure in a redundant drive channel pair a unique ones digit (x1) ID. This setting will enforce hard AL_PAs (unchangeable between fibre channel Loop Initializations [LIPs]) for the drives and facilitate drive loop problem troubleshooting in the event of an error. If the one's digits are not unique, two or more devices will have the same hard AL_PA. In such a case, the DS4700 Express controller will use soft AL_PAs for the devices that have identical hard AL_PAs.

98IBM System Storage DS4700 Express Storage Subsystem: Installation, User’s and Maintenance Guide