Sun Cluster 3.0-3.1 Hardware Administration Manual for Solaris OS

Appendix A Data Replication Approaches

This appendix describes available data replication approaches with Sun Cluster. Host-based data replication is important in all clusters. Storage-based data replication, using special software, provides additional data redundancy for any type of cluster.

This appendix includes the following sections:

Note –

The examples in this appendix illustrate general campus cluster configurations and are not intended to indicate required or recommended setups. For simplicity, the diagrams and explanations concentrate only on features unique to understanding campus clustering. For example, public-network Ethernet connections are not shown.

Using Host-Based Data Replication

A two-room configuration with host-based data replication is defined as follows:

If the room containing the quorum disk is lost, the system cannot recover automatically. Recovery requires intervention from your Sun service provider.

Figure A–1 shows a sample two-room configuration with storage arrays in each room.

Figure A–1 Example Two-Room Campus Cluster With Host-Based Data Replication (No Multipathing)

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Figure 7–7 is similar to a standard noncampus configuration. The most obvious difference is that FC switches have been added to switch from multimode to single-mode fibers.

SPARC: Using Storage-Based Data Replication

Figure A–2 shows a sample two-room configuration where data is replicated between two storage arrays. In this configuration, the primary storage array is contained in the first room, where it provides data to the nodes in both rooms. The primary storage array also provides the secondary storage array with replicated data. During normal cluster operation, the secondary storage array is not visible to the cluster. However, if the primary storage array becomes unavailable, the secondary storage array can be manually configured into the cluster by a Sun service provider.

Note –

As shown in Figure A–2, the quorum device is on an unreplicated volume.

Figure A–2 SPARC: Example Two-Room Configuration With Storage-Based Data Replication

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Storage-based data replication can be performed synchronously or asynchronously in the Sun Cluster environment, depending on the type of application that is used.

To ensure data integrity, use multipathing and the proper in-box RAID. The following list includes considerations for implementing a storage-based data replication, campus cluster configuration. These considerations are not specific to Sun Cluster.

SPARC: Recovery Concerns When Using Storage-Based Data Replication

As with all campus clusters, those that use storage-based data replication generally do not need intervention when they experience a single failure. However, if you lose the room that holds your primary storage device (as shown in Figure A–2), problems arise in a 2–node cluster. The remaining node cannot reserve the quorum device and cannot boot as a cluster member. In this situation, your cluster requires the following manual intervention:

  1. Your Sun service provider must reconfigure the remaining node to boot as a cluster member.

  2. You (or your Sun service provider) must configure an unreplicated volume of your secondary storage device as a quorum device.

  3. You (or your Sun service provider) must reconfigure the remaining node to use the secondary storage device as primary storage. This reconfiguration might involve rebuilding volume manager volumes, restoring data, or changing application associations with storage volumes.