Chapter 3. IBM System Storage DS3500 Storage System planning tasks
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controller are transferred to the alternate controller, which is the configuration setting for
Microsoft Windows, IBM AIX, and Linux (when using the RDAC or SDD driver and
non-failover Fibre Channel HBA driver) systems.
When ADT is disabled, the I/O data path is still protected as long as you use a multi-path
driver. After the I/O data path problem is corrected, the preferred controller does not
automatically reestablish ownership of the logical drive. You must open a storage
management window, select Redistribute Logical Drives from the Advanced menu, and
perform the Redistribute Logical Drives task.
Figure 3-27 shows the ADT-disabled failover mode phases.
Figure 3-27 ADT-disabled mode path failover
Note: In ADT-disabled mode, you are required to issue a redistribution command
manually to get the LUNs balanced across the controllers.
Host / Server
1
0
1
2
3
1
2
3
A
[2]
B
[3]
Fa
ilov
e
r Driv
e
r
X
Application
0
0
Host / Server
1
0
1
2
3
1
2
3
A
[2]
B
[3]
F
a
ilov
e
r Drive
r
X
Application
0
0
Host / Server
1
0
1
2
3
1
2
3
A
[2]
B
[3]
Fa
ilov
e
r Driv
e
r
X
Application
0
0
Host / Server
1
0
1
2
3
1
2
3
A
[2]
B
[3]
Fa
ilov
e
r Driv
e
r
X
Application
0
0
Port 0 receive an error.
connection is no longer
valid, error is passed on
to the failover driver
- 020 failed
- 130 alternate
The failover driver can
now use the alternate
path for any retried or
new I/Os
- 020 failed
- 130 current
Application is using LUN 0
Failover driver hides the
two physical paths to LUN
- 020 current (colored)
- 130 alternate (white)
Failover driver determine
usage of alternate path
to continue I/O. Send a
Mode Select SCSI command
to the storage. Volume
ownership changes as a
result of SCSI mode
select command.
- 020 failed
4
3
2
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Summary of Contents for DS3500
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