What is data deduplication? In this encore episode, Curtis Preston and Prasanna Malaiyandi break down exactly how dedupe works and why it changed backup forever.

We're bringing this one back from the Backup to Basics series because it's one of the episodes listeners came back to again and again — not just a lot of downloads, but people who stuck around for the whole thing.

Curtis has been in the backup industry for over 30 years, and when asked what the single most important development in that time has been, his answer is immediate: deduplication. No close second.
So what actually is it? Curtis and Prasanna walk through the real mechanics — fingerprints, chunks, the dedupe index — and explain why dedupe is a completely different animal than compression, even though people often lump them together.

They also dig into your dedupe domain, which determines how far the system looks for duplicate data. Is it scoped to a single volume? A host? Or is it truly global, comparing data across everything coming in? That scope changes your savings dramatically.

Curtis makes the case that file-level dedupe isn't really dedupe at all — it's single-instance storage wearing a different name. Real dedupe happens at the sub-file, block level.

Then there's the split that shapes entire product categories: source-side dedupe versus target-side dedupe. Curtis explains why source dedupe means redesigning your backup software from the ground up, while target dedupe lets you plug an appliance into whatever you're already running. Prasanna challenges some of the assumptions along the way, and that back-and-forth is a big part of what made this episode land the first time.

By the end, they even cover hybrid dedupe, a concept that splits the difference between source and target and trips up almost everyone the first time they hear it explained.

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 actually understand what your vendor means by "dedupe ratio," this episode 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?

Listen to the full episode and check out more at https://www.backupwrapup.com/what-is-data-deduplication
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