When companies make duplicate copies of enterprise data for backup, disaster recovery or other business purposes, they are said to be replicating data.
Such duplicate copies of data can reside locally on the same system or network segment, or they can be placed in remote locations.
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Replication can take place at the application level or the storage level. Application replication takes place at the transaction level: Each transaction is captured and duplicated on multiple systems. Storage replication involves copying the data that sits under the application.
Organizations replicate and mirror data for a variety of reasons. Since Sept. 11, a major driver for data replication has been disaster recovery and business continuity planning. Companies are hoping to bolster their capabilities in these areas by maintaining copies of data and applications at one or more off-site locations.
Corporations also replicate data to enable wider and quicker access to information across the enterprise. It's quicker to access copies of data stored on local servers than it is to access data stored on a remote server.
Similarly, data is sometimes copied and stored at multiple locations to let multiple business units access it for their individual needs, such as data mining. Development and testing work is also less risky and disruptive when done on a copy rather than on live production data.
"There are a myriad uses for data," says John Young, an analyst at D.H. Brown Associates Inc. in Port Chester, N.Y. "There are more people [than ever before] wanting access to and using data within a business. When you combine that with the standard requirement to back up and store data, it's easy to see what's driving data replication."
There are a variety of methods with which to replicate data from a primary source to secondary sites. The choice depends on the level of protection a company's applications require or the business needs driving the replication effort, says Dianne McAdam, an analyst at Illuminata Inc. in Nashua, N.H.
A financial services company, for instance, is far more likely to need real-time replication than a manufacturing operation, she says. Factors such as cost, complexity and performance impact also affect the choice of replication method, McAdam says.
Synchronous vs. Asynchronous