A frequent question regarding deduplication is “What deduplication ratio does your product provide?” This is a reasonable question, but the complications that go with the answer come from the fact that only part of the ratio is from the product itself. There are a number of environmental factors that can also greatly affect deduplication ratio. So, unfortunately, the correct answer to the question is “it depends…”—a statement that is rarely satisfactory.
Some equipment providers have made their customers unhappy by trying to promise a deduplication ratio based solely on the deduplication technology, not taking into account enough information about the environment in which the technology will be used.
The following should clarify further the environmental factors that can affect deduplication ratio.
1. The amount of duplicate data in the full backup data set
More duplicate data means a higher initial deduplication ratio. This is the leading factor that influences the deduplication ratio of your first backup on a deduplication VTL.
2. Retention
Keeping more full backups means greater opportunity for deduplication over time. This is the leading factor that influences the long-term deduplication ratio that you will achieve with your deduplication VTL.
3. Rate of data change
More change to data over time means less deduplication can occur and this will negatively impact your long-term deduplication ratio.
4. Rate of data growth
More data growth also means less deduplication can occur; therefore, your long-term deduplication ratio will be negatively impacted.
While it is fair to ask what deduplication ratio a VTL can support, it is also important to understand the relative effects of the environmental factors that will ultimately determine your deduplication ratio.
View my whiteboard video on Environmental Factors & Their Effect on Deduplication Ratios
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Jeffrey Graham
Senior Product Manager