IBM DS8000 - Manual (Page 118)

96 DS8000 Series: Concepts and Architecture
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 5-10 shows the concept of LSSs and address groups.
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
Address group X'2x': FB
Address group X'1x' CKD
Extent Pool FB-2
LSS X'10'
LSS X'12'
LSS X'14'
LSS X'16'
LSS X'18'
LSS X'1A'
LSS X'1C'
LSS X'1E'
LSS X'20'
LSS X'22'
LSS X'24'
LSS X'26'
LSS X'28'
LSS X'2A'
LSS X'2C'
LSS X'2E'
LSS X'11'
LSS X'13'
LSS X'15'
LSS X'17'
LSS X'19'
LSS X'1B'
LSS X'1D'
LSS X'21'
LSS X'1F'
LSS X'23'
LSS X'25'
LSS X'27'
LSS X'29'
LSS X'2B'
Ser
ver
0
Extent Pool CKD-1
Rank-a
Rank-b
Extent Pool FB-1
Rank-c
Rank-d
LSS X'2D'
Ser
ver1
Extent Pool CKD-2
Rank-w
Rank-x
Extent Pool FB-2
Rank-y
Rank-z
X'1E00'
X'1E01'
X'2800'
X'1500'
X'1D00'
X'2100'
Volume ID
X'2101'
LSS X'2F'