Article

The pros and cons of host-based data replication software

Jacob Gsoedl

Host-based data replication products for disaster recovery (DR) don't depend on additional hardware components. Their data replication software runs on servers, which makes host-based data

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replication an inexpensive and easy replication method to deploy.

"Deploying host-based replication only requires installing the replication software on source and target servers and you are ready to go," noted Bob Roudebush, director of solutions engineering at Double-Take Software Inc. The replication software is well-suited to work in heterogeneous environments, supporting the widest range of storage options that include both network- and direct-attached storage. While most products support Windows, support for Linux and Unix is more tenuous and, therefore, platform support is clearly one of the critical evaluation criteria when selecting a host-based data replication product.

On the downside, host-based data replication adds processing overhead to servers and the installed replication software carries the risk of introducing unknown behavior. "For critical and high-end application servers, IT managers tend to favor array-based replication over host-based replication because it keeps server resources dedicated to the app and doesn't expose it to potential bugs or flaws in the replication software," said Lauren Whitehouse, an analyst at Milford, Mass.-based Enterprise Strategy Group. Furthermore, licensing costs and system administration duties increase proportionally with the number of servers, giving both array- and network-based replication an advantage in environments with a large number of servers. In addition, visibility in host-based data replication is typically limited to source and target servers. This is very different from the centralized architectures of array- and network-based replication offerings that enable a more holistic view into the data replication infrastructure.

The target markets for host-based data replication products are typically small- to medium-sized businesses (SMBs) that can't afford more expensive replication alternatives. Host-based data replication products enable SMBs to deploy data protection and disaster recovery architectures that, until a few years ago, were only seen in larger firms. CA, Double-Take, InMage Systems Inc., Neverfail Inc. and SteelEye Technology Inc. are some of the vendors that have enabled smaller companies to deploy replication-based disaster recovery and data protection at a fraction of the cost of array- and network-based replication. Although each of these products replicates data from one location to another, they differ in features such as efficiency, bandwidth throttling, management, high-availability failover capabilities, platform support and application integration. Only a thorough product evaluation will reveal which product offers the best fit for a given environment.

In addition to these standalone offerings, data backup software vendors are integrating host-based replication into their backup suites with the hope of expanding their reach into the lucrative remote- and branch-office data protection business.

"We see a convergence of DR and data protection, and consider replication to be a feature and not a standalone product," said Marty Ward, senior director, product marketing for the Data Protection Group at Symantec Corp. Most backup software vendors are already offering host-based data replication options for their backup suites; some examples include BakBone Software Inc.'s NetVault: Real-Time Data Protector; CommVault Continuous Data Replicator (CDR); EMC Corp.'s RepliStor to complement EMC NetWorker; Symantec Backup Exec Continuous Protection Server (CPS); and Symantec NetBackup PureDisk with a deduplication option, as both a standalone product and a NetBackup option.

The main advantage of combining traditional data backups and replication is the ability to manage replicas and backups within a single tool. Aside from their host-based replication options, backup software vendors have been working on integrating their backup suites with leading storage arrays and network-based replication products to enable customers to manage all replicas and backups with the same tool.

This article originally appeared in Storage magazine.

About this author: Jacob Gsoedl is a frequent contributor to "Storage" magazine.


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