IBM DS8000 manual Volume Group

￿They contain one or more host attachments from different hosts and one or more LUNs. This allows sharing of the volumes/LUNs in the group with other host port attachments or other hosts that might be, for example, configured in clustering.

￿A specific host attachment can be in only one volume group. Several host attachments can be associated with one volume group. For example, a port with a WWPN number of 10000000C92EF123 can only reside in one volume group, not two or more.

￿Assigning host attachments from multiple host systems, even running different operating system types, are allowed in the same volume group.

Note: We recommend that you configure one volume group per host. Presently the GUI does not allow you to make more than one volume group per host attachment. If you want multiple volume groups on a single host, the GUI does allow you to make more than one host attachment to a host. This is the way you achieve multiple volume groups on a host.

Volume Group 1	Host	Volume Group 2
pSeries1	Host Attachment	xSeries2

Figure 10-3 Diagram of the relationship of a host attachment to a volume group

In Figure 10-3,we show two volume groups, volume group 1 and volume group 2. A pSeries server with 1 host attachment (four ports grouped in that attachment) resides in volume group 1. The xSeries2 server has 1 host attachment (2 ports grouped into the attachment). The ports are grouped together in one attachment definition. For example, the server, xSeries2 is dual pathed to the LUNs through one attachment group definition.

￿In order to share LUNs across multiple host attachments, LUNs can be in more than one volume group as shown in the example in Figure 10-4 on page 196.

Chapter 10. The DS Storage Manager - logical configuration 195