This research document analyzes Plakar, a French open-source backup startup founded in Paris in September 2024 by Julien Mangeard (former CTO of Veepee) and Gilles Chehade (creator of OpenSMTPD). After a $3 million raise in May 2025 from prestigious investors (Olivier Pomel of Datadog, Solomon Hykes of Docker), Plakar joined the Linux Foundation and the CNCF in January 2026.

The architecture rests on three layers: an immutable, parallelized storage layer, a repository layer handling local compression and encryption with an index for deduplication, and a snapshot layer organizing data through a virtual file system backed by a custom B+ tree. The Kloset engine forms the technological core, with its principles of immutable storage, self-describing snapshots, modular connectors, and cryptographic auditability.

The FastCDC algorithm reaches 8,149 MB/s versus 614 MB/s for Restic's Rabin, i.e. 13x faster. The cryptography was audited by Jean-Philippe Aumasson in February 2025, concluding with a "cryptographically sound design." The post-audit algorithms include Argon2id for password derivation (256 MB of memory), AES-256-GCM-SIV resistant to nonce errors, and BLAKE3 for hashing.

The .ptar format, announced in June 2025, modernizes tar (1979) with random access, native S3 support, and deduplication. An illustrative test: archiving 8.8 GB twice produces 18 GB with tar.gz versus 8.2 GB with .ptar.

The benchmarks claim a 60x improvement on S3 (14 minutes to 13 seconds) and a 91.4% storage reduction through deduplication (327 GB → 28 GB for 10 backups). Against Restic (27k GitHub stars), Plakar offers an integrated web interface and non-blocking garbage collection. Against Borg, Plakar provides native S3 support (Borg requires SSH) and a simpler learning curve.

The ISC license (OpenBSD style) guarantees a permanent commitment to open source. French media coverage is enthusiastic (Korben: "atomizes Restic and Borg"), but the absence of international coverage (Germany, Netherlands, Japan) reflects the project's recent nature.

For organizations oriented toward S3/AWS and DevOps teams seeking a sovereign French solution, Plakar warrants serious evaluation, with a recommended trial period on non-critical workloads while the ecosystem matures.