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196 DS8000 Series: Concepts and Architecture
Figure 10-4 Example of volume groups, LUNs and host attachment definitions
In Figure 10-4 we 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.
Host System A
2
Host Attachment
WWPN
WWPN
Host Attachment
WWPN
WWPN
Host System B
1
3
5
4
6
8
7
Volume Group 1
Volume Group 2 Volume Group 3
Host Attachment
WWPN
WWPN
Host System C
Host Attachment
WWPN
WWPN
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.