GAD can show two devices at primary and secondary sites to the host as the same device. This enables the host to access the two sites at the same time. By using this function, you can migrate the UR environment between the primary and secondary sites to different primary and secondary sites without stopping the I/O operations from the host while keeping the UR pairs.
Note: I/O operations from the host need to be
temporarily stopped if switching to the redundant path is not available. For example,
depending on the specifications of the high-level configuration of the storage system
(including the operating system and the mulit-path software), the path to a different WWN
might not be recognized as the redundant path.
Change the configuration from Figure 1 to 2 by performing the following steps:
- Specify a volume used for a UR P-VOL at the source primary site as a P-VOL of a GAD pair, and then create a GAD pair.
- Wait until the GAD pair status becomes PAIR.
- Specify a volume used for an S-VOL for the GAD pair as a target UR P-VOL, and then create a UR pair.
- Wait until the target UR pair status becomes PAIR.
- The target UR is ready for the operations, and then start the I/O operations to the S-VOL of the GAD pair.
Change the configuration from Figure 2 to 3 to complete the migration by performing the following steps:
- Stop the I/O operations to the P-VOL of the GAD pair.
- Specify the S-VOL for the GAD pair, and then suspend (swap suspend) the GAD pair.
- Delete the source UR pair.
- Specify the S-VOL for the GAD pair, and then delete the GAD pair.