Specifications

54 Implementing UPS Configurations with Microsoft Cluster Server
Figure 53. Two UPS units with application handling
This setup looks very similar to Figure 52 on page 53. The important difference is
the one-to-one relation between UPS status and server status. In Figure 52, the
status of a server is determined by the status of two UPS units, but the server can
communicate with one UPS only. In this setup, however, each UPS influences the
status of one server only. Each server monitors its own UPS. If the server
receives a power loss signal, it always begins to shut down.
The way to handle applications on this node depends on the status of the other
node. The other node may be:
1. Unaffected by the power failure (remaining available for cluster applications).
2. Unavailable (powered off, crashed, or unresponsive for other reasons).
3. Available but cannot be the target of a resource move operation.
4. Affected by a power loss but still running.
In terms of MSCS, status 1 corresponds to Node Up. This is the only status
where the node can receive cluster resources. Status 2 means Node Down, not
responding to a cluster heartbeat. Status 3 is Node Paused. A paused node may
run cluster applications, but it will not accept more resources than currently
owned. This can be used by the administrator to prevent overload or prepare for
maintenance.
Status 4 is outside of MSCS’s scope, but the time interval between UPS power
loss and node shutdown is similar to Node Paused: The node is still running, but
the node should not start additional applications. Thus we set a node that
received the power loss signal to Node Paused.
Because the two cluster nodes are supplied by independent power lines, there is
a chance that a power loss in one phase causes one node only to shut down.
Cluster
UPS 1
Phase A
Phase B
Server 1
UPS 2
Server 2
Communications - smart signaling cable
Communications - smart signaling cable