Subsystem Performance Recommendations
The physical relationship between the disk drives and the adapters in an SSA loop can
affect the performance of the subsystem. The guidance below helps you to get best
performance from your subsystem.
The following sequence enables you to determine the best relationship between the
disk drives and the adapter on an SSA loop that contains a IBM Advanced
SerialRAID/X Adapter.
1. Determine which data is accessed most frequently.
2. Assign that data to those disks drives that are farthest (round the loop) from the
adapter connectors. By doing this, you prevent the activity of the busiest disk drive
from obstructing the data path to the other disk drives.
For example, if a loop contains 16 disk drives, and the adapter connectors are between
disk drives 1 and 16, the most-frequently-accessed data should be on disk drives 8 or 9
as shown in Figure 6.
Adapter
Adapter
SSA Disk Drives
Figure 5. Two Adapters Connected in Two SSA Loops
D is k
1
D is k
2
D is k
3
D is k
4
D is k
5
D is k
6
D is k
7
D is k
8
D is k
9
D is k
10
D is k
11
D is k
12
D is k
13
D is k
14
D is k
15
D is k
16
A
dapt
er
Figure 6. Physical relationships
Appendix A. Connecting SSA Devices to the Adapter
35
Summary of Contents for Advanced SerialRAID/X
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