att_abstract={{With the explosion of data in applications all around us, erasure coded storage has emerged as an attractive alternative to replication because even with significantly lower storage overhead, they provide better reliability against data loss. Reed-Solomon code is the most widely used erasure code because it provides maximum reliability for a given storage overhead and is flexible in the choice of coding parameters that determine the achievable reliability. However, reconstruction time for unavailable data becomes prohibitively long mainly due to network bottlenecks. Some proposed solutions either use additional storage or limit the coding parameters that can be used. In this paper, we propose a novel distributed reconstruction technique, called Partial Parallel Decoding (PPD), which divides the reconstruction operation to small partial operations and schedules them on multiple nodes already involved in the data reconstruction. A distributed protocol then runs to progressively reconstruct the unavailable data blocks and this reduces the network pressure. Theoretically, our technique can complete the network transfer in ⌈(log2(k + 1))⌉ time, compared to k time needed for a (k, m) Reed-Solomon code. Our experiments show that PPD reduces repair time and degraded read time significantly. Moreover, our technique is compatible with existing erasure codes and does not require any additional storage overhead. We demonstrate this by overlaying PPD on top of two prior schemes, Local Reconstruction Code and Rotated Reed-Solomon code, to gain additional savings in reconstruction time.
	att_authors={rp267p, mr047v},
	att_copyright_notice={{(c) ACM, 2015. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Eurosys {{, 2016-04-18}}.
	author={Subrata Mitra and Rajesh Panta and Moo-ryong Ra and Saurabh Bagchi},
	institution={{ACM Eurosys}},
	title={{Partial-Parallel-Decoding (PPD): A Distributed Technique for Repairing Erasure Coded Storage}},