We wanted to see how well our PACS data (dicom files primarily) deduplicates. Two separtate n3400 systems each had nearly identical 3TB LUNs carved out of 12TB flexvols. Nothing else existed on the volume. The 3TB LUN was approx 80% full. I took one of the two systems, and deduped it. The results left me perplexed. Before running the dedupe, df -h showed the volume as ~3085GB used (that is also what the 2nd, untouched system is still showing). However, after the dedupe, it is reporting 5290GB used. There has been only minimal new data written to the LUN on that volume. When I run df -h -s, I again see 5290GB used, with 838GB saved (14%). That ratio is good, but the end result is I haven't apparently saved any space, instead I've lost space, approximately 2TB of space!
Can anyone shed light as to why the numbers are showing what they are showing?