HP StorageWorks Enterprise Virtual Array Cluster FIO Starter Kit Guida Utente Scaricare il pdf (Pagina 38)

Figure 7 Single VSM dual-port configuration

Figure 8 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 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.

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HP StorageWorks Enterprise Virtual Array Cluster FIO Starter Kit Guida Utente Pagina 38