content_image/987139.jpg
Figure 1-2 illustrates these two concepts. Detailed differences are described in the following sections. 

<img src='content_image/987139.jpg'>

## Internal-managed 

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: 

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. 

## External-managed 

In an external-managed environment, the operating system has no information about whether it is part of a cluster. 

## 1.1.2 Outage-related differences 

Highlights of this environment include these items: 

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. 

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. 

