Data Deduplication with Hashing: How It Works
How systems use hash digests to identify duplicate data, the tradeoffs of hash-based deduplication, and collision risk at scale.
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Tags: security, hashing, storage
Data Deduplication With Hashing: Finding Duplicate Files Every large collection of files eventually accumulates duplicates. Photos imported from multiple devices, documents copied between folders, build artifacts, backups of backups. Manual deduplication is hopeless at scale. Hashing makes it systematic: compute the SHA-256 of every file, group files by identical hashes, and you have found every exact duplicate — regardless of filename, location, or metadata. Why Hashes Work for Deduplication Two files are identical if and only if their contents are identical. A cryptographic hash function maps file contents to a fixed-length digest such that: Identical contents always produce identical hashes Different contents produce different hashes (with overwhelming probability) The mapping is…
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