Installation guide

If, however, disk drive modules are connected into the link between two SSA

attachments that are in the same using system, those disk drive modules become

isolated both SSA attachments fail, or are held reset, but remain powered on (see also

“Bypass Note” on page 36). In Figure 23, disk drive modules 13 through 16 have been

connected between the SSA attachments of using system 1. If both attachments fail, or

are held reset, but remain powered on, disk drive modules 1 through 12 can still

communicate with using system 2. Disk drive modules 13 through 16, however, cannot

communicate with using system 2, because their data paths are through using

system 1. When using system 1 is rebooted, disk drive modules 13 through 16 remain

unavailable for a long time.

Using System 1

A1 A2 B1 B2 A1 A2 B1 B2

Disk

Using System 2

B2 B1 A2 A1 B2 B1 A2 A1

Figure 23. Disk Drive Modules Isolated by Failing SSA Attachments

Appendix A. Example Configurations 37