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Background

PowerHA Geographic Mirroring replicates independent auxiliary storage pool (IASP) via IBM i networking. As the system writes data from main memory to disk, the same data is sent over TCP/IP to the target system to be written to disk, ensuring identical data between both systems. As a result, Geographic Mirroring provides the same simplicity as SAN-based replication, with the flexibility to work with any storage (internal or external), and is highly efficient.Geographic Mirroring supports replication between up to six nodes across two sites. Replication within a site is synchronous; replication across sites can be either synchronous or asynchronous.

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Code Block
CRTCRG CRG(GEOCRG) 
       CRGTYPE(*DEV) 
       RCYDMN((MN01 *PRIMARY *LAST MN ('192.0.2.100' '192.0.2.101'))
              (MN02 *BACKUP  1     MN ('192.0.2.110' '192.0.2.111'))
              (IA01WI01 *BACKUP  2     WI ('192.0.2.200' '192.0.2.201'))
              (IA02WI02 *BACKUP  3     WI ('192.0.2.202' '192.0.2.203'))) 
       CFGOBJ((MYIASP *DEVD *ONLINE))

...

For additional information on customizing automatic failover, see the QCST_CRG_CANCEL_FAILOVER policy.

Enhanced Automatic Failover with Cluster Monitor

In environments where automatic failover is desired, it is possible to enhance automatic failover to monitor for additional events via a Hardware Management Console (HMC) using cluster monitors. See Advanced Node Failure Detection for additional information.

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  1. End the cluster resource group to configure replication to the next node. For example: ENDCRG CRG(GEOCRG)

  2. Use the Configure Geographic Mirroring (CFGGEOMIR) command to configure Geographic Mirroring replication to the additional node. For this example, the following command is used:

    Code Block
    CFGGEOMIR ASPDEV(MYIASP) 
          ACTION(*CREATE)
          DELIVERY(*ASYNC) 
          COMPRESS(*RESYNC) 
          TGTNODE(IA01WI01)

    This command configures Geographic Mirroring for the IASP named MYIASP to the node IA01WI01.
    Since IA02 WI01 is in a different site from the production system and is the lowest numbered node at that site, it is possible to specify asynchronous delivery, enabling further distances between the nodes.

  3. Since *SELECT was specified for the disk units, a panel showing all non-configured units is displayed on the target node. Use option 1 to select the disk units you want from the list.
    After confirming the selection, PowerHA will initialize and format the disk units on the target system and configure Geographic Mirroring.
    Since the default value for the start indicator parameter was left as *YES in the command, PowerHA will also start do the following:

    1. Start the cluster resource group

    2. While the production copy did not need to be varied off, if it had been varied off, the start parameter value of *YES will also vary on the IASP on the production system

    if it was not already varied on, and start replication

    1. .

  4. This example would repeat this process starting at step 1 for the final node IA02WI02. With IA02WI02, a delivery value of *SYNC must be specified since synchronous replication will be used between the systems within the IA site containing nodes IA01 WI01 and IA02WI02.

Results

Geographic Mirroring is now configured between the nodes in the CRG. To verify and monitor the status of replication, use the Display ASP Session (DSPASPSSN) command. For example, DSPASPSSN SSN(GEOMIRSSN).