Selecting BC/DR solutions
In planning Business Continuity/Disaster Recovery systems, businesses can select from a wide range of data protection solutions. The choices they make will be determined by the importance of the information they need to protect (i.e. its time sensitivity and business value) and the amount of money they are willing to spend to protect it. These factors help determine appropriate the recovery time objective (RTO).
Industry research shows that a typical mid-sized to large enterprise might have 150 mission and time-critical applications that require continuous availability; 300 or so applications that require data restoration within 4 to 24 hours; and 100 or so non-critical applications that can wait as long as several weeks for data restoration.
Levels of information protection
If a business cannot continue profitable operations without its data, it usually implements a remote hot site that completely duplicates critical data and applications and makes them continuously available. The cost of such a solution is justified by the cost to the business of even a few minutes of down time. At the other end of the spectrum is business data that may not need to be restored for days, weeks or even longer after a data center disruption. In fact, some business data requires no restoration at all but simply needs to be protected for legal and archival purposes.
The most cost-effective enterprise-wide BC/DR plan will probably involve a mixture of disk and tape technologies, from the most expensive for data that needs to be continuously available to less expensive technologies for data of less time sensitivity and importance.
New factors and increased focus in BC/DR planning
BC/DR strategies are affected by the increasing amount of business data being pushed into the mission-critical category, requiring continuous availability. Businesses are also aware that the dangers to their mission-critical data are greater than ever before. Not so long ago businesses had to plan for human error, technical glitches and, of course, natural disasters. Post 9/11, businesses must also plan for terrorist attacks that, as a November 2002 report from analyst firm Illuminata put it, could "take out more than just a couple of floors of one data center."
Indeed, government agencies and private disaster planners are urging businesses to establish BC/DR systems that separate primary and backup sites by at least 200 miles, instead of the typical 60 miles. The SEC and Federal Reserve are calling for businesses that play a significant role in financial markets to establish fully redundant backup sites at least 300 miles offsite and be able to recover critical activities on the same business day of a disaster.
Tape backup market
The evolution toward networked storage, the heightened awareness of Business Continuity and Disaster Recovery planning and the need to reduce costs and improve efficiencies throughout IT, is stimulating the market for cost-effective tape and enterprise backup solutions.
IDC (September 2001) sees the tape market moving from solutions targeting the high end of the data storage market to lower-cost solutions that add more capacity than standalone tape drives. Through 2003-2004, as data volumes increase 200%-300% per year, Meta Group (October 2001) projects that backup/restore windows will be reduced using intelligent storage, highly parallel tape solutions, and FC-based SANs.
In a March 2001 note, Gartner Group stated unequivocally that disk-based replication will not replace tape backup. Tape's low cost -- it is about 10 to 60 times less expensive than disk storage -- makes it a compelling economic argument for its inclusion in any high-availability storage infrastructure.
Tape backup and its historical limitations
Tape backup plays a big role in cost-effective BC/DR systems since it is significantly less expensive than disk-based replication and is perfectly appropriate for protecting many types of business information. However, historically there have been inherent performance problems with tape backup over distance that limited its role in BC/DR planning.
The primary reason for this limited role is the sequential nature of tape I/O operations, which makes tape backup highly sensitive to the latency that accompanies distance. Unlike disk-based operations in which blocks can be written in parallel, tape I/O for a single block must complete before the next block can be written. Figure 3 illustrates the typical tape performance falloff with distance for several popular tape products. As the chart makes plain, remote tape backup systems simply don't have the throughput to move large amounts of data over distances of more than a few miles.
About the author
Patty Barkley, storage networking market manager, joined CNT in December 1999 and has more than 16 years of professional experience in sales and marketing of storage networking solutions. She is responsible for marketing CNT's storage networking products, services and solutions to its global customers and business partners. Barkley has more than 14 years of experience in various sales and marketing management capacities. Prior to joining CNT, she worked for Network Systems Corporation and StorageTek.