Figure 1-2 illustrates these two concepts. Detailed differences are described in the following  sections. In an internal-managed environment, the operating system or the application has information  that it is part of a cluster. In most cases. HA components are installed that check whether the  cluster partners, hardware, and software components are reachable or available. Highlights of this environment include these items: In an external-managed environment, the operating system has no information about whether  it is part of a cluster. Highlights of this environment include these items: Independent of the selected architecture (internal- or external-managed), there are two main  forms of outages:  planned outages  and  unplanned outages . In this section, we describe the  differences between internal and external-managed architectures regarding these two types  of outages. 4  Implementing IBM VM Recovery Manager for IBM Power Systems 1.1.2 Outage-related differences External-managed Internal-managed Figure 1-2 Internal- and external-managed HA and DR GLYPH<SM590000> Can be used on physical or virtual systems. GLYPH<SM590000> Has a hot-standby topology. GLYPH<SM590000> Is based on independent operating systems. GLYPH<SM590000> Cluster logic is part of the OS or application. GLYPH<SM590000> Rolling migration is possible. GLYPH<SM590000> Supports active/passive and active/active architecture within the cluster. GLYPH<SM590000> Requires a virtual system.  GLYPH<SM590000> Has a cold-standby topology. GLYPH<SM590000> Is based on a single operating system. GLYPH<SM590000> Cluster logic is outside of the OS or application. GLYPH<SM590000> Supports only an active/inactive architecture within the cluster. GLYPH<SM590000> Offers reduced license costs.