Pairs Of Adapter Connectors In The Loop - Some Shared Data - IBM Advanced SerialRAID Adapters SA33-3285-02 User Manual

Pairs of Adapter Connectors in the Loop – Some Shared Data
The following sequence enables you to determine the best relationship between the
disk drives and the adapter on an SSA loop that contains two or more pairs of adapter
connectors. Some of the disk drives share data access with other disk drives.
1. For each pair of connectors, identify all the data that the loop is to access.
2. For each pair of connectors, identify the data that the loop is to access most
frequently.
3. Assign the data for each pair of adapter connectors to the disk drives that are
connected immediately next to the pair of connectors in the loop. Assign the
most-frequently-accessed data to those disk drives that are farthest from the
adapter connectors. By doing this action, you prevent the activity of the busiest disk
drive from obstructing the data path to the other disk drives.
For example, the loop that is shown in Figure 13 contains 16 disk drives. The
connectors of adapter A are between disk drives 1 and 16, and the connectors of
adapter B are between disks 8 and 9. Therefore:
v Adapter A should access disk drives 1 through 4 and disk drives 13 through 16. The
most-frequently-accessed data should be on disk drives 4 and 13.
v Adapter B should access disk drives 5 through 8 and disk drives 9 through 12. The
most-frequently-accessed data should be on disk drives 5 and 12.
Figure 13. Pairs of Connectors in the Loop – Some Shared Data
Disk Disk Disk
1 2 3
Disk Disk Disk
16 15 14
Disk Disk Disk
4 5 6
Disk Disk Disk
13 12 11
Chapter 2. Introducing SSA Loops
Disk Disk
7 8
Disk Disk
10 9
25