IBM RS6000 - 7026 - H70 Service Manual

Also see for RS/6000 7025 F50 Series: User guide Service guide Service guide

Loops and Data PathsAll devices that are attached to an SSA adapter card are connected through SSAlinks. See Figure 3-2 on page 3-60. The SSA links are configured as loops. Dataand commands to a particular device pass through all other devices on the linkbetween the adapter and the target device.Data can travel in either direction around a loop. The adapter can, therefore, accessthe disk drive modules through two data paths. The using system cannot detectwhich data path is being used.If a disk drive module fails, or is turned off, the loop is broken, and one of the datapaths to a particular module is no longer available. The disk drive modules on theloop continue to work, but an error is reported to the using system.Figure 3-3 shows that disk drive module in slot 3 has failed. The disk drive modulesin slots 1 and 2 can communicate with the using system only through connector A1of the SSA adapter. The disk drive modules in slots 4, 5, and 6 can communicateonly through connector A2 of the SSA adapter.Figure 3-3. Disk Drive Module in Slot 3 Has Failed3-62 Service Guide