Cardano Leios Reworks Node Storage After Sixfold Testnet Result

Input Output’s consensus team reported changes to the Ouroboros Leios prototype on September 25, focusing on data storage and node operation. The update builds on results from MusashiNet, where the proposed Cardano consensus upgrade completed its first public test phase under sustained transaction load.

Leios Separates Reversible and Settled Data

The prototype now stores data that could be rolled back separately from data that has settled. Certified endorser blocks move between the two database files in the background, and node operators can place each file on a different disk.

The team also changed how the node removes obsolete records. It marks them first, then deletes them in paced batches so database cleanup does not block the node. Development tools can now build a Leios chain with blocks and votes, or cut that chain back to a selected slot and remove transactions left outside it.

These changes address the storage and recovery demands created by Leios’s additional blocks. They give the team a more robust prototype for the next round of sustained testing.

MusashiNet Measured Sixfold Throughput

Leios is designed to expand Cardano’s transaction capacity while retaining the Praos chain. Block producers create additional endorser blocks to carry transactions, which pass through committee certification before entering the permanent ledger. The design is specified in CIP-164.

MusashiNet’s first phase, Earth, ran for 41 days. More than 127,000 blocks were produced, around 30,000 endorser blocks were announced, and nearly 8,000 certificates appeared on-chain. Sixty-three stake pools registered during the test.

With Leios active, the testnet peaked at 26.8 TxkB/s, compared with 4.51 TxkB/s for Praos at current Cardano mainnet parameters. TxkB/s measures the volume of transaction data processed per second, not the number of transactions. During Earth’s more stable final days, Leios carried 54% of the traffic reaching the testnet chain.

The test also exposed software problems, including memory leaks, stalled synchronization and delays in block production under load. Fixes from that phase and further changes to the mempool are being tested as MusashiNet progresses through its Water phase.

Mainnet Preparation Moves Beyond the Speed Test

Input Output aims to produce a mainnet-ready Leios release candidate by late 2026. The remaining work covers production-grade implementation, conformance and security testing, integration with Cardano node software, and preparation across stake pools and ecosystem tools. A hard-fork decision will determine when the upgrade can be activated.

The Leios roadmap calls for published measurements of throughput, latency and node resource use under sustained load. It also requires testnet upgrades and a plan for gradually increasing mainnet parameters. Those results will determine how the performance measured in Earth translates into operating requirements and an initial mainnet configuration.