What is data deduplication, and why does Curtis call it the single most important development in backup over the last 30 years? In this encore episode, W. Curtis Preston and Prasanna Malaiyandi break down exactly how dedupe works, why it's not the same as compression, and why the fine print of your dedupe domain determines how much storage you actually save.

This episode originally aired as part of the Backup to Basics series, and it's back because listeners couldn't get enough of it — not just downloads, but people who stuck around for the whole conversation, some more than once. That says something, because this isn't a surface-level explainer. Curtis and Prasanna get into fingerprints, dedupe indexes, and the real-world tradeoffs between file-level and block-level dedupe.

You'll hear why Curtis argues that file-level dedupe isn't "real" dedupe at all, just single-instance storage wearing a costume. Then the conversation shifts to the split that shapes entire product categories: source-side dedupe versus target-side dedupe. Curtis walks through why source dedupe requires you to essentially replace your backup software, while target dedupe lets you bolt an appliance onto whatever you're already running. Prasanna pushes back on some of the assumptions along the way, which is exactly the kind of back-and-forth that made this episode stick with listeners the first time around.

By the end, they even get into hybrid dedupe, a concept that splits the difference and confuses almost everyone the first time they hear about it.

If you've ever wondered why your backup storage doesn't need to be 30 or 40 times the size of your production data, or you just want to finally understand what your backup vendor means when they throw around terms like "dedupe ratio," this is the episode that clears it up.

Chapters:

00:00 – Intro

08:10 – What Is Data Deduplication?

12:24 – Dedupe vs. Compression

16:13 – Fingerprints and the Dedupe Index

16:52 – What's a Dedupe Domain?

19:48 – Is File-Level Dedupe Really Dedupe?

21:53 – Source Dedupe vs. Target Dedupe

28:20 – What Is Hybrid Dedupe?