I saw this little quote on Techtarget today: "File-level deduplication will save a relatively small amount of space on your disk/tape archive. Block-level deduplication will save more space on your disk/tape archive, and variable block-level deduplication will save even more space on your disk/tape archive." For those of you interested in reading the whole article, it can be found here (registration required).
While the statement is true, it is a little light on detail, and downplays the importance and impact of the different technology choices. By way of setting expectation, we could expect the following deduplication ratios when backing up the same data set with the same retention ratios:
- File level deduplication: 3:1 to 5:1
- Fixed block level deduplication: 5:1 to 10:1
- Variable block level deduplication: 30:1 or better