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Chapter 10. The DS Storage Manager - logical configuration 191
Figure 10-1 Diagram of hosts and host attachment groups
In Figure 10-1 we show three pSeries hosts with four host ports each. The first host,
pSeries1, has no specific attachment groupings, so each port could be defined as an
attachment. Server ports can be grouped in attachments for convenience. For example,
pSeries2 shows two host attachments, with two ports in each attachment. Server pSeries3
shows one host attachment with four ports grouped in the one attachment.
A host attachment can be configured to access specific disk subsystem I/O ports or all
valid disk subsystem I/O ports.
Host attachments can be configured to access specific volume groups.
A specific host attachment (one port or set of grouped ports) can access only one volume
group.
Multiple host attachments, even different open system host types, with the same block
size and addressing mode, can access the same volume group. The safest approach to
this concept is to configure one host per volume group. If shared access to the LUN is
required, for example, for dual pathing or clustering, then the shared LUNs may be placed
in multiple volume groups as shown in Figure 10-3 on page 195.
FICON/ESCON attachment access is controlled by zSeries HCD/IOGEN definitions.
Some ESCON/FICON attachment considerations follow.
– One storage subsystem FICON host definition will be needed in order to configure I/O
adapters to use FICON protocol instead of FCP protocol.
– No storage subsystem host definition will be required for ESCON hosts since ESCON
adapters are single purpose and do not require configuration.
– Default volume groups are automatically created, allowing anonymous access for
ESCON/FICON.
pSeries1
pSeries2
pSeries3
NO Host Attachment Group defined
for host pSeries1. By default,
the 4 ports are placed in 4 Host
Attachments
Two Host Attachment Groups defined
for host pSeries2
One Host Attachment Group defined
for host pSeries3
Fiber Channel
Port
W
W
P
N
1
W
W
P
N
2
W
W
P
N
3
W
W
P
N
4
W
W
P
N
5
W
W
P
N
6
W
W
P
N
7
W
W
P
N
8
W
W
P
N
9
W
W
P
N
1
0
W
W
P
N
1
1
W
W
P
N
1
2