Lakestream: A Consistent and Brokerless Data Plane for Large Foundation Model Training

2026-05-11

AI Summary

Existing large model training data pipelines struggle to simultaneously ensure batch semantics, fault isolation, and consistency. This work proposes an agent-free, object-storage-native training data plane featuring three core innovations: a Transactional Global Batch (TGB) abstraction that guarantees training consistency, a storage-layer-embedded garbage collection mechanism aligning producer states with distributed checkpoints, and a communication-free Decentralized Adaptive Commit (DAC) algorithm. Leveraging lakehouse ACID semantics in object storage and distributed checkpointing, the system achieves higher throughput than colocated loaders and Kafka, lower read latency, and full fault isolation across 64-GPU multimodal pretraining and supervised fine-tuning (SFT) workloads.

Abstract

Modern Large Foundation Model (LFM) training has transformed the data pipeline from a static ingestion layer into a dynamic component that must co-evolve with the training process. Existing systems are ill-equipped: colocated dataloaders offer no failure isolation, while message queue-based disaggregated dataloaders operate on a record/offset abstraction that cannot express the batch-level semantics required by distributed training. We present Lakestream, a brokerless, object-store-native training data plane with three key properties. First, it introduces the Transactional Global Batch (TGB), which builds on lakehouse-style ACID storage semantics and extends them with training-specific consistency, including atomic all-rank batch visibility, a globally ordered step sequence, checkpoint-aligned lifecycle management, and end-to-end exactly-once recovery. Second, it realizes recovery and retention directly in the storage layer, by inlining producer state in the manifest and tying reclamation to distributed checkpoint state. Third, its Decentralized Adaptive Commit (DAC) algorithm sustains stable ingestion throughput as the manifest grows, without any inter-producer communication. Evaluations on large-scale multimodal pre-training and SFT workloads using 64 GPUs show that Lakestream outperforms colocated dataloader throughput while providing full failure isolation, outperforms Apache Kafka in ingestion throughput, and achieves lower consumer read latency than Kafka.

Problem

• Large Foundation Model training
• data pipeline
• batch-level semantics
• failure isolation
• distributed training

Innovation

• Transactional Global Batch
• brokerless data plane
• Decentralized Adaptive Commit
• lakehouse-native storage
• exactly-once recovery