HP StorageWorks SAN Virtualization Services Platform administrator guide (5697-0204, January 2010)

If the DPM pair is in an active/passive relationship (a relationship used in all HP SVSP releases up
to and including v2.1), only the paths through the active DPM for a virtual disk are used at any given
time while passive paths are used only in failover scenarios. The number of front-end paths that a host
can have through a single DPM is directly dependent on the number of host ports in the configuration
that are zoned to that DPM.
Since the DPM is a shared resource with finite capacity, it can only handle a finite number of front-end
paths (see the product release notes for the maximum number of paths and volumes supported by HP
SVSP). For example, a configuration with only a single host can allow the host to have the maximum
number of front-end paths to the DPM (one path to each DPM front-end port). If there are a large
number of hosts connected to the DPM then having the maximum number of front-end paths for each
host is not always the best configuration since it can lead to reduced performance due to the increased
contention for shared resources. The following recommendations are made to balance capacity and
performance in the overall configuration:
• Each host port has at most two front-end paths to each DPM along each fabric. This is a recom-
mended limit of eight front-end paths for each host with four front-end paths through each DPM.
• Limit the number of DPM target ports in each DPM-Host zone to one quad on a single DPM.
• Use one operating system in each individual DPM-Host zone. This can be done by implementing
only single initiator port zones as previously discussed in the zoning guidelines.
Figure 11 illustrates zoning between a single server with two dual-port HBAs and the first two quads
of a DPM pair with the recommended limit of eight front-end paths. Paths between server initiator
ports and DPM front-end target ports are color coordinated to represent the different zones to which
they belong within the red and blue fabrics.
Figure 11 Zoning from server to two quads of a DPM pair
.
It is common for multiple hosts to be zoned to the same DPM front-end target ports, particularly in
larger configurations where the number of host ports outnumber the DPM ports.
Figure 12 illustrates zoning between two servers with single dual-port HBAs and the first two quads
of a DPM pair with the servers being isolated from each other by being zoned to different quads on
each DPM.
Zoning50