IBM H SERIES RS/6000 - Manual (Page 212)

Example 3. Broken Loop (Disk Drive Module Removed): The following
diagram shows eight disk drive modules connected to connectors A1 and A2 of the
SSA adapter, but the loop is broken because disk drive module in slot 3 has been
removed. Four disk drive modules are connected to connectors B1 and B2 of the
same SSA adapter.
Although the missing disk drive module is reported as an error, all the remaining disk
drive modules can still communicate with the using system. Two disk drive modules
can communicate through connector A1 of the SSA adapter. Five disk drive
modules can communicate through connector A2 of the SSA adapter. Five disk
drive modules can communicate through connectors B1 and B2 of the same SSA
adapter (normal loop).
7-52 RS/6000 Enterprise Server Model H Series User's Guide