HP 3PAR Policy Server Administrator's Guide (QR483-96003, December 2012)

HP 3PAR Policy Server 5-5
Using Redundant Agent Gateways with Policy Server
To help you understand redundant gateways, let's start with non-redundant gateway operations. Normally, in
a non-redundant gateway configuration, a given managed asset is associated with one Agent gateway. The
Agent gateway sends asset data (data items, alarms, for example) to the HP 3PAR Enterprise Server on
behalf of the managed asset, as well as receives and executes actions that are sent from the Enterprise Server
to the managed asset.
In a redundant gateway configuration, a managed asset may be associated with more than one Agent
gateway. The Agent gateways with which a managed asset is associated are called redundant Agent
gateways. Redundant Agent gateways are logically connected to the managed asset throughout the entire
runtime. However, they do not communicate with each other, nor are they aware of each other’s existence.
In other words, a redundant Agent gateway has no indication that it is a part of a redundant gateway
configuration. It is configured in exactly same manner as a regular, non-redundant Agent gateway.
Although it recognizes the association of a managed asset with multiple Agent gateways, the HP 3PAR
Enterprise Server treats the redundant Agent gateways equally. None of the Agent gateways that manage an
asset is considered primary, so when an action is pending for the managed asset, it is delivered by the Agent
gateway that contacts the Enterprise Server first. When another redundant Agent gateway contacts the
Enterprise Server, even if it happens immediately after contact from the first Agent gateway, the pending
action is not delivered.
When a redundant gateway configuration is used, the managed asset must actively publish its data to an
associated Agent gateway. Moreover, the managed asset is responsible for selecting the Agent gateway to
which to publish the data. Otherwise, the data is going to be duplicated when it reaches the Enterprise
Server.
Communication with Policy Server in a Redundant Gateway Configuration
In a non-redundant rateway configuration, HP 3PAR Policy Server delivers policies upon a contact from the
asset. However, unlike messages regarding requested actions, which must be delivered only once, policies
must be delivered to each Agent gateway that manages a given asset. Otherwise, the policies are not
enforced properly. Therefore, Policy Server delivers the policy for a managed asset to all Agent gateways
that are managing that asset.
Important! If more than one Agent gateway is managing an asset, it is assumed that all managing Agent
gateways are using the same Policy Server. If not, conflicting policies and unpredictable results are
likely to occur.