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Write-order fidelity

To use the Secondary in a disaster recovery scenario, write-order fidelity must be maintained. The term write-order fidelity means that VVR tracks writes on the Primary in the order in which they are received and applies them on the Secondary in the same order. It is important to maintain write-order fidelity to ensure that the data on the Secondary is consistent with the data on the Primary. While the data at the Secondary can be behind in time, it must be a consistent image of the Primary RVG at a point in the past.

Without write order fidelity, there is no guarantee that a Secondary has consistent, recoverable data. VVR maintains write-order fidelity regardless of the mode of replication and across all the data volumes in an RVG. For example, in a database environment, the log and data space are typically on different volumes. On the Primary, VVR applies writes to the log and data spaces in a fixed order and maintains this fixed order when applying the writes on the Secondary. If write-order fidelity is not maintained, a database application may not recover successfully when failed over to the Secondary.