Streamlining distributed Deep Learning I/O with ad hoc file systems

With evolving techniques to parallelize Deep Learning (DL) and the growing amount of training data and model complexity, High-Performance Computing (HPC) has become increasingly important for machine learning engineers. Although many compute clusters already use learning accelerators or GPUs, HPC storage systems are not suitable for the I/O requirements of DL workflows. Therefore, users typically copy the whole training data to the worker nodes or distribute partitions. Because DL depends on randomized input data, prior work stated that partitioning impacts DL accuracy. Their solutions focused mainly on training I/O performance on a high-speed network but did not cover the data stage-in process, for example. We show in this paper that, in practice, (unbiased) partitioning is not harmful for distributed DL accuracy. Nevertheless, manual partitioning can be error prone and inefficient. Typically, data must be unpacked and shuffled before it is distributed to nodes. We propose a solution that features both: efficient stage-in and fast access to a global namespace to prevent biases. Our architecture is based around an ad hoc storage system relying on a high-speed interconnect allowing an efficient stage-in of DL data sets into a single global namespace. Our proposed solution does not limit access to parts of the data set or relies on data duplication, also relieving the HPC storage system. We obtain high I/O performance during training and ensure minimal interference with communication of the learning workers. The optimizations are transparent to DL applications and their accuracy is not affected by our architecture.