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Beware of reduction ratio reports from vendors. In a recent survey, ESG found that among survey participants using dedupe technology, most reported reduction ratios in the 10x to 20x range (see "Capacity reduction," this page). Data reduction rates vary depending on a number of factors, such as data type, change rate and retention period, and whether or not dedupe occurs across multiple data sets.
A vendor could accurately claim reduction ratios of more than 100x, but some explanation of that number would be required. For example, calculating deduplication ratios for client-side deduplication of a full backup in a low change-rate environment, such as a Windows, could result in 100x daily reduction ratios. However, this isn't the reduction ratio for backup storage and is a great example of a liberty vendors take when issuing quantifiers. You should ask your deduplication vendor for the method used to arrive at their reduction ratio number.
Dedupe improves the value proposition of disk-based data protection because it eliminates the redundancy traditionally seen in secondary storage processes. Given the explosive growth rates of data and the cost of power and cooling, implementing dedupe is becoming an imperative.
Choosing a deduplication strategy isn't a simple task. Technology maturity varies considerably and the vendor landscape is changing quickly
| with new entrants and a recent spate of acquisitions. As solutions are considered, cut through the vendor hype by requesting real-world references and proof points. Test backup performance and, more importantly, restore performance. Conducting your performance testing and due diligence early should save you from unnecessary drama later on.
This was first published in June 2008