IBM H SERIES RS/6000 - Manual (Page 210)

Example 2. Broken Loop (Cable Removed): Each disk drive module normally
communicates with the adapter through one data path. Because data can pass
around the loop in either direction, however, the adapter automatically reconfigures
the loop to enable communication to continue to each disk drive if the loop becomes
broken.
In the following diagram, eight disk drive modules should be connected to connectors
A1 and A2 of the SSA adapter. However, the loop is broken because the SSA cable
has been disconnected from connector A2. Four disk drive modules are connected
to connectors B1 and B2 of the same SSA adapter.
Although the broken loop is reported as an error, all the disk drive modules can still
communicate with the using system. The eight disk drive modules can communicate
through connector A1 of the SSA adapter . The five disk drive modules can commu-
nicate through connectors B1 and B2 of the same SSA adapter (normal loop).
7-50 RS/6000 Enterprise Server Model H Series User's Guide