ProactiveCache: On Reducing Degraded Read Latency of Erasure Coded Cloud Storage

Erasure coding is gaining attraction in cloud storage systems because it improves data reliability with huge cost savings in terms of storage. However, data recovery in erasure codes includes high disk I/O, network traffic and complex decoding that impacts degraded read latency, in case of failures. Data access latency is one of the most important metrics to determine Quality of Service. Reducing degraded latency in erasure coding is vital to improve user performance. To reduce degraded read latency of erasure codes, in this paper, we have proposed a cache based technique called ProactiveCache. This proactively copies objects in failure predicted machine into a cache tier. To deploy ProactiveCache, cloud storage system should employ various failure prediction methods to predict hardware failures. On accurate failure predictions, ProactiveCache eliminates degraded read latency. For evaluation, ProactiveCache is implemented on Ceph object storage. Experimental results show that Proactive-Cache reduces degraded read latency up to 38% and improves throughput by 37%.