Redundancy transitioning enables erasure-coded storage to adapt to varying performance and reliability requirements by re-encoding data with new coding parameters on-the-fly. Existing studies focus on bandwidth-driven redundancy transitioning that reduces the transitioning bandwidth across storage nodes, yet the actual redundancy transitioning performance remains bottlenecked by the most loaded node. We present BART, a load-balanced redundancy transitioning scheme that aims to reduce the redundancy transitioning time via carefully scheduled parallelization. We show that finding an optimal load-balanced solution is difficult due to the large solution space. Given this challenge, BART decomposes the redundancy transitioning problem into multiple sub-problems and solves the sub-problems via efficient heuristics. We evaluate BART using both simulations for large-scale storage and HDFS prototype experiments on Alibaba Cloud. We show that BART significantly reduces the redundancy transitioning time compared with the bandwidth-driven approach.

Many organizations own data but have limited machine learning expertise (data owners). On the other hand, organizations that have expertise need data from diverse sources to train truly generalizable models (model owners). With the advancement of machine learning (ML) and its growing awareness, the data owners would like to pool their data and collaborate with model owners, such that both entities can benefit from the obtained models. In such a collaboration, the data owners want to protect the privacy of its training data, while the model owners desire the confidentiality of the model and the training method that may contain intellectual properties. Existing private ML solutions, such as federated learning and split learning, cannot simultaneously meet the privacy requirements of both data and model owners.