• LUN or Consistency Group of LUNs import details


    LUN or Consistency Group of LUNs import details

    LUN or Consistency Group of LUNs import work flow

    All LUN or Consistency Group (CG) import operations are executed from the target Unity storage system.

    Prerequisites for a LUN or CG import session

    Before starting a LUN or CG import session, the following conditions must be met:

    1. The source VNX system exists, and the VNX1 Block OE is 5.32.x or later or the VNX2 Block OE is 5.33.x or later.
    2. (Optional) The specified name for the import session is not used by other import sessions.
    3. SAN Copy is enabled on the source VNX system.
    4. The source LUN or CG exists.
    5. The source LUN or CG is not under import or has an associated complete import.
    6. Depending on the type of import connection that is used between the source and target systems:
      • For an import using an FC-based connection, FC ports are cabled and ports zoning is configured between the VNX and Unity storage systems.
        Avoid ports that are used for host traffic and MirrorView. On the VNX, SAN Copy and MirrorView configured on the same ports do not operate. Import connections cannot be configured. Configure and cable the source SPA FC_1 and SPB FC_1 ports to the target SPA FC_1 and SPB FC_1 ports for SAN Copy. Also, avoid ports that are used for synchronous replication.
      • For an import using an iSCSI-based connection, iSCSI interfaces are configured on both the source and target systems.
        • Configure iSCSI IP interfaces on SPA and SPB on the source system. Avoid MirrorView reserved iSCSI ports for block import iSCSI interfaces.
        • Configure iSCSI IP connections between the source and target systems and verify the connection configuration.
      • Once the import connections are created, the following has occurred:
        • Management IP connectivity and VNX Admin credentials are verified.
        • VNX SAN Copy FC or iSCSI initiators are discovered and registered.
        • All block resources on the source system that are eligible for import are discovered.
        The discovered objects and their relationships persist.
    7. A reserved LUN pool (RLP) is configured:
      The size of the RLP LUN created for a source LUN is recommended to be 20% of the size of the source LUN.
      • For the import of a single LUN, one RLP LUN is configured.
      • For the import of a CG of LUNs, one RLP LUN is configured for each LUN in the CG.
      An RLP LUN is not tagged to a source LUN for a specific feature. When an RLP LUN is added to an RLP that is intended for a source LUN, it is possible that a completely different SnapView or other SAN Copy session can consume the newly added RLP LUN. It is recommended that other features like SnapView and MirrorView/A are stopped during import.
    8. Configure hosts on the target system the same as the hosts or storage groups on the source system.
      For iSCSI hosts, the hosts should log in to the target system to register the host initiators on the target system.

    Start a LUN or CG import session

    The import session is automatically started after creation in the Unisphere UI.

    For UEMCLI or REST, the UEMCLI command and REST operation of start are shared with the same command and operation of resume to align with the behavior of VDM import and replication. If the import start fails, the import state is kept as Initial Copy with a Minor failure health state and the health details being set to The import session failed to provision target resource. At this time, you can fix the problem by getting detailed information from the job and tasks and then resume the import session.

    The start of an import session is an asynchronous operation by default and always returns a success after creating a backend job to run the initial copy. Before the start of the import, a pre-check is done.

    In the event of a system reboot, import sessions are paused and resume automatically when the system returns. Affected LUNs may fail over to the peer SP. If a LUN is failed over, it would need to be failed back and the session resumed.

    LUN or CG import initial copy

    When the import session starts, it enters the initial copy state. The target resource (LUN or CG) is automatically created on the selected target pool from the respective source LUN or CG and balanced between the target SPs. The SAN Copy limits that are configured on the source system are used to schedule syncs:

    1. From the current SP of the LUN or LUNs in the import session, separate lists are created for SPA and SPB LUNs from which to find the counts for each SP.
    2. If there are available differential sync slots from the concurrent SAN Copy sync limits, the slots are allocated so from SPA and SPB and the session is changed from the Pending to Syncing state.
      Once slots from SPA and SPB are allocated to an import session, no other session can take those slots until either the session is canceled or completed. If the session is canceled or completed, the slots are distributed to either existing sessions (if they can benefit from it) or new pending sessions.
    3. Once the import session reaches below the cutover threshold (percentage of data remaining to be copied), the session is changed from the Syncing to Ready for Cutover state.

    LUN or CG import cutover

    When the initial copy has completed, the LUN or CG import session enters the Ready to Cutover state. Before you run the cutover operation, ensure that the import session exists and is in the Cutover Ready state.

    You can launch cutover from either Unisphere, UEMCLI, or REST. Cutover starts a job, which does the following:

    • Host access on VNX Source system for source LUN or LUNs is disabled for all hosts by removing source LUN or LUNs from Host SGs.
      It is required that all Host I/O be paused before cutover is issued.
    • Differential sync for SAN Copy session is run to sync the last delta.
    • SAN Copy session is deleted.
    • Host access to target LUN or LUNs is enabled for the selected hosts that are configured on the target system.