APC AP9606 Specifications download pdf (Page 61)

Chapter 3. UPS configurations for cluster 53

Figure 52. Two UPS units without application handling

But connecting the power cords in this way prevents correct application handling.

Communication is possible only between one server and one UPS. Therefore, if a

server receives a UPS signal, software on this server cannot check the power

status of the second UPS. For example, phase B fails. Server 2 gets the signal

from UPS 2. Should server 2 begin to shut down? For this decision, information

about UPS 1 would be needed but is not available. Even if server 2 always

decides for shutdown, a question would remain about bringing the applications

offline or moving them to server 1.

This solution is appropriate when application handling is not required and the

focus is on redundant power. An example is a file server cluster; losing power

without executing an ordered shutdown is a risk for data consistency.

Figure 53 shows better cabling, which we recommend for correct UPS

communication.

Cluster

UPS 1

Phase A

Phase B

Server 1

UPS 2

Server 2

Communications - smart-signaling cable

1 2 ... 56 57 58 59 60 61 62 63 64 65 66 ... 95 96

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APC AP9606 Specifications Page 61