IBM DS8000 manual Host System C, Address groups

	Host System A
Host Attachment		Host Attachment
WWPN	WWPN	WWPN	WWPN

Host System B

Host Attachment

WWPN WWPN

Host System C
Host Attachment
WWPN	WWPN

	1	4	5	7
2	3		6	8

It is possible to have several host attachments associated to one volume group.

We do recommend, for ease of management, to associate only one host attachment to each volume group.

Volume Group 1 Volume Group 2 Volume Group 3

Figure 10-4 Example of volume groups, LUNs and host attachment definitions

In Figure 10-4we show three hosts (host A, host B, and host C) defined in the logical configuration as three different host systems. The user will group the WWPN of each host system in groups called host attachments. As shown in the diagram, each host attachment is assigned to one volume group. Volumes can belong to several volume groups. For example, volumes 5 and 6 are in volume group 2 and volume group 3, so they will be shared by host A, host B, and host C. Several host attachments can be associated to the same volume group. For example, hosts B and C will share volumes 5, 6, 7, and 8 because their host attachments are assigned to the volume group 3. However, for management simplification, we recommend that only one host attachment is assigned to each volume group.

￿The maximum number of volume groups for the DS8000 is 8320.

Address groups

An address group is a group of FB or CKD LSSs. An address group has up to 16 LSSs.

The DS8000 supports up to 16 address groups. Each address group is identified by one hexadecimal digit: address group 0 to address group F.

LSS/LCU

A logical subsystem (LSS) is a topological construct that consists of a group of up to 256 logical volumes. The DS8000 architecture allows up to 255 LSSs (hex 00 to FE). However, at GA, a DS8000 will allow you to have up to 64 CKD logical subsystems (16384 CKD logical volumes) and up to 64 fixed-block logical subsystems (16384 fixed-block logical devices). There is a one-to-one mapping between a CKD logical subsystem and a zSeries control-unit image. ESCON-attached hosts can only access LSSs 00 to 0F, so these should be reserved for CKD LSSs if you plan to use ESCON host adapters.

196DS8000 Series: Concepts and Architecture