Unplanned outage of Site 2 (H2 MM secondary) and return to three-site configuration

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In this scenario, an unplanned outage of Site 2 (H2) occurs. Disaster Recovery capability is still required, so a Global Mirror session must be set up between Site 1 (H1) and Site 3 (H3) while Site 2 is down. Procedures are shown for both the multi-target Metro Mirror - Global Mirror session type as well as the Metro Global Mirror cascaded session type.

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Follow these steps to carry out this scenario.

Procedure for Multi Target Metro Mirror - Global Mirror session type

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Procedure

  1. Start H1->H2 H1->H3

    Issue this command to begin multi-target replication when the production I/O is running on H1. Once the session is in a Prepared state, both sites 2 and 3 will have a consistent copy of the data

    Note: Production I/O to H1 can continue during the following steps.
  2. Unplanned outage of H2
    This event causes an unplanned outage of H2, which causes the session to go Suspended (Partial).
    Note: Replication has stopped from Site 1 to Site 2, however, replication will automatically continue from Site 1 to Site 3. No user action is necessary. When Site 2 is available, continute to the next step to get back into full three site mode.
  3. Start H1->H2 H1->H3

    Issue this command when H2 is ready to be brought back into the configuration. This command restores the original configuration. Production I/O can continue on H1. Once the session reaches a Prepared state, a consistent copy will reside on Site 2 and Site 3.

Procedure for Cascaded Metro Global Mirror session type

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Procedure

  1. Start H1->H2->H3

    Issue this command to begin Metro Global Mirror on your system when the production I/O is running on H1. Once the session is in a Prepared state, both sites 2 and 3 will have a consistent copy of the data

    Note: Production I/O to H1 can continue during the following steps.
  2. Unplanned outage of H2

    This event causes an unplanned outage of H2, which causes the session to go suspended. It is recoverable if the session was in a Prepared state when the outage occurred. If the session state was Preparing, the session might be recoverable at Site 2 but would not be recoverable at Site 3.

  3. Start H1->H3

    This command starts a Global Mirror session between Site 1 and Site 3 during the outage of H2. Production I/O can continue on H1.

    Note: If you are running DS8000® devices on H1 with the proper level of microcode, and enough time has passed since the initial start of the session, the creation of the H1 to H3 pairs will NOT require a full copy.

    Once the session has reached a Prepared state, a consistent copy of the data will reside on Site 3.

    Note: Data on Site 2 is no longer consistent at this point.
    Note: After Site 2 has been successfully brought back up, perform the next step to return to the three-site configuration.
  4. Start H1->H2->H3

    Issue this command when H2 is ready to be brought back into the configuration. This command restores the original configuration. Production I/O can continue on H1. Once the session reaches a Prepared state, a consistent copy will reside on Site 2 and Site 3.