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Data recovery and protection are the top most priorities of business today and essential elements of any business continuity strategy?the bigger the enterprise, the more challenging the problem?requiring robust and reliable solutions. Final choices and IT decisions depend on how a business perceives its tolerance for data inaccessibility or loss. As such, protection can be as simple as backup of the information locally to a secondary storage device, or it can be complex, involving clustered application and database servers from multiple sites replicating data continuously to other secure remote sites over a long distance.
In response to the dilemma of choice, this document presents an easy-to-mange failover and failback recovery option available for Oracle 10g data stored in storage area networks (SANs) and looks at three strategies for replicating Oracle databases over long distances between primary and remote HP StorageWorks XP arrays. The strategies focus on two different technologies and approaches?one using a real-time array-based replication of data across long distances, the other using a host and log-based replication system that updates data at intervals. Each strategy has it own advantages and disadvantages that address enterprise storage and replication requirements. This paper also looks at a third approach that integrates the two technologies into a single replication solution and considers the benefits of this combined strategy.
To validate these solutions, the HP StorageWorks Customer Focused Testing team (CFT) has tested Oracle 10g databases with Real Application Clusters (RAC) for replication, failover, and recovery across primary and remote SAN sites running Red Hat Enterprise Linux Advanced Server. The first phase of the testing used the array-based replication capabilities of HP StorageWorks Continuous Access XP along with other HP component software and firmware. The second phase of the tests used Oracle Data Guard, a host and network, and the third phase used a combination of both. This paper presents the results of these tests, along with best practices and recommendations for 'best fit' scenarios.
Note that the configuration used in the test environment is only one of many possibilities that could have been selected. Oracle was selected as being the most popular and widely deployed enterprise database software, and HP Storage Works XP arrays as the 'best-of-breed' storage arrays available in the market today. Both are well tested and well known for their reliability and dependability.
For your convenience, a list of all hardware and software equipment appears in Appendix A. All recommendations and best practices are derived from the test procedures and results presented in this document.
Introduction
Each of the following replication technologies offers specific advantages as part of a complete SAN replication solution. The following section reviews the HP Continuous Access XP and Oracle Data Guard products and how they replicate Oracle 10g data. It also describes the role of other software products used in the test configurations and test procedures.
HP Continuous Access XP solution
HP StorageWorks Continuous Access XP software is a high-performance, real-time remote data mirroring solution for replication between XP disk arrays. It is platform, operating system, and application agnostic. Integrated with Oracle 10g RAC, Continuous Access provides fast bi-directional failover and failback recovery that results in reliable data protection and sustained business continuity.
The Continuous Access XP solution for replication of Oracle SANs, as presented in this document, is hardware/array-based and utilizes block-level replication over Fibre Channel?as this is fast and provides high-level data consistency. Using Continuous Access XP connectivity, the HP StorageWorks XP12000 Disk Array is capable of running nearly full speed even while a remote mirroring operation is simultaneously in progress on the array. Array-based replication has little impact on server performance because the data is replicated directly between the arrays without requiring CPU compute cycles.
When replicating data over long distances, the choice of asynchronous and synchronous copy modes enables Continuous Access XP to meet the most demanding requirements for data currency and system performance. In asynchronous mode, Continuous Access XP completes the write I/Os at the local site without waiting for it to be written to the cache of the remote XP disk array. This optimizes performance at the local site, especially when replicating data over long distances.
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