Chapter 4. IBM System Storage DS planning and configuration 141
Figure 4-11 shows the phases of failover in the AVT-enabled case.
Figure 4-11 AVT-enabled mode path failover
4.5 Operating system restrictions
In your planning, you should also consider the restrictions of your operating system. In this
section, we cover the maximum file system size ordered by operating system and their
commonly used file systems, the maximum number of LUNs that can be assigned to one
host, and the maximum logical volume size supported by various operating systems.
Note: In AVT mode, RDAC automatically redistributes the LUNs to their preferred path
after the failed path is operational again.
The failover driver will
choose to use the
alternate path for any
retired or new I/Os.
- 020 failed
-130 current
Host / Server
1
1 3
1
3
A
[2]
B
[3]
X
Application
0
Host / Server
1
0
1 3
1
2
3
A
[2]
B
[3]
X
Application
0
0
The LUN 0 volume
transfers to controller B
which currently has I/O
activity for that volume.
- 020 failed
-130 current
3
4
0
20
2
2
Phase
1-2 see Figure 4-10
Failover Driver
Failover Driver
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