Chapter 12
Remote Replication
Key Concepts
Remote replication is the process to create replicas of information assets at remote sites (locations). Remote replication helps organizations mitigate the risks associated with regionally driven outages resulting from natural or human-made disasters. During disasters, the workload can be moved to a remote site to ensure continuous business operation. Similar to local replicas, remote replicas can also be used for other business operations.
This chapter discusses various remote replication technologies, along with three-site replication and data migration applications. This chapter also covers remote replication and VM migration in a virtualized environment.
12.1 Modes of Remote Replication
The two basic modes of remote replication are synchronous and asynchronous. In synchronous remote replication, writes must be committed to the source and remote replica (or target), prior to acknowledging “write complete” to the host (see Figure 12.1). Additional writes on the source cannot occur until each preceding write has been completed and acknowledged. This ensures that data is identical on the source and replica at all times. Further, writes are transmitted to the remote site exactly in the order in which they are received at the source. Therefore, write ordering is maintained. If ...
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