Freeze your files.
Thaw when it matters.
Frostholm is a CLI for incremental, deduplicated, encrypted file archival. Built after I lost four years of photography to a failing drive.
Why Frostholm
Content-addressed dedup
CDC chunking with BLAKE3 hashing. 100 GB of documents typically stores as 12–18 GB of unique chunks after a few snapshots.
Encrypted at rest
ChaCha20-Poly1305 with Argon2id key derivation. Your repository password never leaves your machine.
Cold-tier backends
Local filesystem, S3-compatible, and Backblaze B2. Costs under $0.006/GB/month on B2 Glacier-equivalent.
Fast selective restore
Restore a single file or subtree from any snapshot without downloading the full archive. The index stays warm in a local cache.
Quick tour
Initialize a repository, run a snapshot, and verify integrity — three commands, under 10 seconds.
Recent posts
Frostholm v0.4: Backblaze B2 backend and faster chunking
The biggest release yet — native B2 support, a new FastCDC chunker, and 30% better throughput on large trees.
How content-addressed deduplication works inside Frostholm
A deep dive into CDC chunking, BLAKE3 hashing, and the pack-file format that makes cold storage practical.
Frostholm vs restic vs Borg: a realistic benchmark
A year-end performance comparison on a 180 GB photo library. Where each tool wins and where it struggles.