HP StorageWorks SAN Virtualization Services Platform Administrator Guide (5697-0934, May 2011)

Figure 10 Host server dual-port configuration
DPM-host zoning
A DPM-Host front-end zone is used to give a host access to the virtual disks created in HP SVSP
and presented through the DPM front-end target ports. A front-end path between the DPM and the
host consists of a single host port and a single DPM front-end port. The following rules must be
applied when creating DPM-Host zones:
• Each host port on a single host is zoned to exactly one front-end target port from each DPM.
Zoning to a port from each DPM allows for failover capabilities if the active DPM fails or the
particular active front-end port fails. Having front-end ports from multiple DPMs is allowed
since each DPM front-end port is strictly a target port in HP SVSP and has no interaction with
other DPM ports.
• Each host port on a single host is zoned to a different port on a given DPM. Zoning multiple
ports on a host to a single DPM front-end port leaves the configuration vulnerable to a loss of
availability if the DPM port fails.
Using the rules described, each zoned host port has exactly two front-end paths to a presented
virtual disk with one front-end path through each DPM.
If the DPM pair is in an active/passive relationship (a relationship used in all HP SVSP releases
up to and including v3.0), 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
recommended 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 (page 37) 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.
36 Zoning