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One Loop with Two Adapters in Each of Two Using Systems
If the loop contains four SSA adapters, with two adapters in each of two using systems,
disk drives become isolated if they are connected between the two adapters of one
using system, and both those adapters fail, or are held reset, but remain powered on.
Bypass Note: Your SSA Disk Subsystem, or SSA Disk Enclosure, might contain
bypass cards. Each bypass card can switch the internal strings of the
subsystem, or enclosure, if it detects that neither of its connectors is
connected to a powered-on SSA adapter or device. Therefore, if the two
SSA adapters fail, or are held reset, but remain powered on, the bypass
card does not operate, and the disk drives become isolated. (For more
information about bypass cards, see the publications for your disk
subsystem or enclosure.)
In Figure 6, SSA adapters 1 and 2 are in using system 1; SSA adapters 3 and
4 are in using system 2. In each using system, the two adapters are connected to
each other.
If the two SSA adapters of either using system fail, or are held reset, but remain
powered on, all the disk drives can still communicate with the other using system.
UsingSystem1
A1 A2 B1 B2 A1 A2 B1 B2
Disk
1
Disk
2
Disk
3
Disk
4
Disk
5
Disk
6
Disk
7
Disk
8
Disk
12
Disk
11
Disk
10
Disk
9
Disk
16
Disk
15
Disk
14
Disk
13
1
2
UsingSystem2
B2 B1 A2 A1 B2 B1 A2 A1
3
4
Figure 6. One Loop, Two Adapters in Each of Two Using Systems
12 User’s Guide and Maintenance Information