IBM DS8000 manual Volume access, Address groups

Address groups

Address groups are created automatically when the first LSS associated with the address group is created, and deleted automatically when the last LSS in the address group is deleted.

LSSs are either CKD LSSs or FB LSSs. All devices in an LSS must be either CKD or FB. This restriction goes even further. LSSs are grouped into address groups of 16 LSSs. LSSs are numbered X'ab', where a is the address group and b denotes an LSS within the address group. So, for example X'10' to X'1F' are LSSs in address group 1.

All LSSs within one address group have to be of the same type, CKD or FB. The first LSS defined in an address group fixes the type of that address group.

zSeries clients that still want to use ESCON to attach hosts to the DS8000 should be aware of the fact that ESCON supports only the 16 LSSs of address group 0 (LSS X'00' to X'0F'). Therefore this address group should be reserved for ESCON-attached CKD devices, in this case, and not used as FB LSSs.

Figure 5-10shows the concept of LSSs and address groups.

		Address group X'1x' CKD
		LSS X'10'		LSS X'11'
		LSS X'12'		LSS X'13'
		LSS X'14'		LSS X'15'
	Extent Pool CKD-1	LSS X'16'	X'1500'		Extent Pool CKD-2
		LSS X'18'
	Rank-a			LSS X'17'		Rank-w
		LSS X'1A'
		LSS X'1C'		LSS X'19'
	Rank-b	X'1E00'		LSS X'1B'		Rank-x
				LSS X'1D'
Server0		X'1E01'				Server1
			X'1D00'
		LSS X'1E'
	Extent Pool FB-1			LSS X'1F'	Extent Pool FB-2
	Rank-c					Rank-y
	Rank-d	Address group X'2x': FB
		LSS X'20'		LSS X'21'	Extent Pool FB-2
		LSS X'22'	X'2100'			Rank-z
		LSS X'24'
			X'2101'
		LSS X'26'
				LSS X'23'
		X'2800'
				LSS X'25'
		LSS X'28'		LSS X'27'
	Volume ID			LSS X'29'
		LSS X'2A'		LSS X'2B'
		LSS X'2C'		LSS X'2D'
		LSS X'2E'		LSS X'2F'

Figure 5-10 Logical storage subsystems

The LUN identifications X'gabb' are composed of the address group X'g', and the LSS number within the address group X'a’, and the position of the LUN within the LSS X'bb'. For example, LUN X'2101' denotes the second (X'01') LUN in LSS X'21' of address group 2.

5.3.7 Volume access

A DS8000 provides mechanisms to control host access to LUNs. In most cases a server has two or more HBAs and the server needs access to a group of LUNs. For easy management of

96DS8000 Series: Concepts and Architecture