Data Guard based replication vs. SAN (EVA5000 & CA) based replication

Business continuance expert Pierre Dorion answers a reader's question: What are the pros and cons of Data Guard based replication vs. SAN (EVA5000 & CA) based replication?

What are the pros and cons of Data Guard based replication vs. SAN (EVA5000 & CA) based replication?
To answer this question, it must first be assumed that when you say EVA5000 and "CA," you are referring to and Oracle database stored on EVA5000 disk storage and replicated offsite using CA's XOsoft WANSynchHA for Oracle. When compared at a high-level, both methods offer similar features and much more than array based replication because they both are application aware. In comparison, simple disk array based replication requires extra steps to ensure that the database remains consistent during the replication process. For example, any type of "snapshot like" replication requires that the database be aware of the operation (typically briefly quiesced) to establish a clear point-in-time relationship with subsequent database changes (i.e.: redo logs). Some of the advantages of Data Guard over WANSynchHA include:
  • Synchronous replication (in addition to asynch)
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  • Redo apply to a physical replica or SQL apply to a logical replica
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  • Replication to up to nine standby databases
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  • Offers the ability to choose between three protection modes (Maximum Protection, Maximum Availability and Maximum Performance) to fit specific business requirements
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  • Seamless "role switching" from primary to standby between databases.
However, cost must be taken into consideration. Data Guard is part of Oracle Enterprise and, unless an organization is already licensed for Enterprise, can add significant implementation costs. It should also be noted that at this point, XOsoft WANSynchHA Oracle is a Windows-based solution. Oracle Data Guard runs on Oracle on supported platforms and integrates with Oracle RAC, Flashback and RMAN.

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