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Data replication tools for disaster recovery

On the surface, data replication tools represent an efficient strategy for disaster recovery (DR). A data replication approach relies on ferrying updates, transactions and changes

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across a network -- from a primary production server to a secondary backup server. If the primary server goes down, the secondary server can take over when a failover operation kicks in.

For companies whose recovery time objective (RTO) and recovery point objective (RPO) for regaining business-critical functionality is a matter of minutes, data replication is a truly workable strategy. However, in researching vendors for replication tools, it soon becomes apparent that there are a few catches with the best and most workable data replication tools:

  • The core for any data replication system is the data replication software, along with the links and hardware necessary for primary and secondary systems to maintain constant contact and communication. Some of the major players in this arena include Dell Inc. EqualLogic (iSCSI SAN arrays remote replication facility), Double-Take Software Inc., EMC Corp. (SRDF/A and MirrorView/A) and NetApp Inc. (SnapVault and SnapMirror).
  • Where replication data volumes are significant or part of heavy wide-area network (WAN) traffic, a vital component in any Internet-based solution is some kind of WAN accelerator. Over time, the cost of bandwidth for replication becomes a major factor. Consequently, all of the major WAN accelerator players, including Blue Coat Systems Inc., Cisco Systems Inc., Juniper Networks Inc., Riverbed Technology Inc. and Silver Peak Systems Inc. have extensive partnerships with the leading replication players.
  • Likewise, replication touches deeply into any enterprise's storage infrastructure, particularly where server farms, data centers or cluster/grid computing environments are involved. That's why you see storage vendors doing replication business (EMC and Dell/EqualLogic), and why so many other data storage vendors (Brocade Communications Systems Inc., Emulex Corp. and Symantec Corp. and major system vendors like Dell, Fujitsu Inc., Hewlett-Packard (HP) Co., IBM Corp. and Sun Microsystems Inc.) often come into this picture as well. It's possible to get into this market for as little as $20,00 to $30,000 (two WAN endpoints with accelerators, plus replication software). Organizations with more WAN endpoints, and lots of servers will probably end up spending $8,000 to $10,000 per endpoint and approximately $1,000 per server for software (but can drop the endpoint costs for solutions that integrate with existing WAN accelerators).

Data replication and WAN accelerators

Given that the cost of bandwidth can easily consume 30% or more for annual data replication budgets, making the most of Internet bandwidth between primary and secondary systems looms very large in the minds of disaster recovery and business continuity (BC) planners. This also explains why so many enterprises build data replication solutions around combinations that work with their existing WAN and server infrastructures, which together dictate what kinds of replication solutions get purchased and deployed.

Sometimes, when always-on or hot recovery sites are contracted from third-party suppliers, those site operators will specify replication solutions. Because duplicating IT assets essentially means multiplying IT costs by the number of recovery sites set up, this gets expensive fast. This also explains why it's crucial to limit recurring costs for any replication solution -- where bandwidth and personnel costs quickly swamp equipment and software outlays. As you examine your options for data replication, the most important considerations that emerge will most often come from a systems integration perspective. After that, you'll also want to compare features and functions, talk to reference accounts and make sure your candidates solutions will work well in your production environments, often through a pilot test of some kind.

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Very few companies have the luxury of crafting such solutions from scratch, and must work with or around existing components and technologies. That's what makes replication so interesting for those businesses and organizations that decide they need it for disaster recovery or business continuity reasons. It's not a difficult option to elect, as much as it can be a challenging option to implement. That's why working from the WAN accelerator out to the servers and storage elements appears to be the most commonly practiced and productive approach.

Take Silver Peak Systems as an example of this approach. Its Data Replication offerings embrace a range of offerings, including EMC, NetApp, Double-Take, Dell/EqualLogic and Symantec. Thus, companies with existing investments in those tools and technologies will find it easy to add (or build upon) Silver Peak WAN accelerators as part of a coherent data replication strategy. Similar investigations of Cisco, Riverbed, Blue Coat and Juniper Networks offerings will turn up similar alliances and concomitant possibilities for implementation. That said, it's probably a good idea to carefully manage your costs for software and integration to prevent them from ballooning out of control.

Ultimately, the best data replication solution is one that integrates most easily (and inexpensively) with existing infrastructure investments, and that shows itself to support BC/DR planning recovery objectives. Because the WAN accelerator components are so important to controlling recurring costs for data replication, they will often drive other elements that come into this picture. That's why we recommend that you start with your WAN accelerator vendor when it comes to scoping out a suitable solution, or that you base your choice of WAN accelerator at least in part on the data replication options that it supports.

About this author: Ed Tittel is a long-time freelance writer and trainer who specializes in topics related to networking, information security, and markup languages. He writes for numerous TechTarget.com Web sites, and recently finished the 4th edition of The CISSP Study Guide for Sybex/Wiley (ISBN-13: 978-0470276886).


This was first published in May 2009

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