Given the ever-increasing size of supercomputers, fault resilience and the ability to tolerate faults have become more of a necessity than an option. Checkpoint-Restart protocols have been widely adopted as a practical solution to provide reliability. However, traditional checkpointing mechanisms suffer from heavy I/O bottleneck while dumping process snapshots to a shared filesystem. In this context, we study the benefits of data staging, using a proposed hierarchical and modular data staging framework which reduces the burden of checkpointing on client nodes without penalizing them in terms of performance. During a checkpointing operation in this framework, the compute nodes transmit their process snapshots to a set of dedicated staging I/O servers through a high-throughput RDMA-based data pipeline. Unlike the conventional checkpointing mechanisms that block an application until the checkpoint data has been written to a shared filesystem, we allow the application to resume its execution immediately after the snapshots have been pipelined to the staging I/O servers, while data is simultaneously being moved from these servers to a backend shared filesystem. This framework eases the bottleneck caused by simultaneous writes from multiple clients to the underlying storage subsystem. The staging framework considered in this study is able to reduce the time penalty an application pays to save a checkpoint by 8.3 times.
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- Can Checkpoint/Restart Mechanisms Benefit from Hierarchical Data Staging?
Dhabaleswar K. Panda
- Springer Berlin Heidelberg