IBM Advanced SerialRAID Adapters SA33-3285-02, User Manual

Page: 423 / 531

Example 2. Broken Loop (Cable Removed)
Each disk drive normally communicates with the adapter through one data path.
Because data can pass round the loop in either direction, the adapter automatically
reconfigures the loop to enable communication to continue to each disk drive if the loop
becomes broken.
In Figure 57 on page 404, disk drives 1 through 8 should be connected to connectors
A1 and A2 of the SSA adapter
1
, but the loop is broken because the SSA cable has
been disconnected from connector A2. Disk drives 9 through 12 are connected to
connectors B1 and B2 of the same SSA adapter. Disk drives 13 through 16 are
connected to connectors A1 and A2 of a different SSA adapter
2
.
Although the broken loop is reported as an error, all the disk drives can still
communicate with the using system. Disk drives 1 through 8 can communicate through
connector A1 of the SSA adapter
1
. Disk drives 9 through 12 can communicate
through connectors B1 and B2 of the same SSA adapter (normal loop); disk drives 13
through 16 can communicate through connectors A1 and A2 of the SSA adapter
2
.
Chapter 17. SSA Service Aids
403