att_abstract={{The reliability of erasure-coded distributed storage
systems, as measured by the mean time to data loss (MTTDL),
depends on the repair bandwidth of the code. Repair-efficient
codes provide reliability values several orders of magnitude
better than conventional erasure codes. Current state of the art
codes fix the number of helper nodes (nodes participating in
repair) a priori. In practice, however, it is desirable to allow
the number of helper nodes to be adaptively determined by
the network traffic conditions. In this work, we propose an
opportunistic repair framework to address this issue. It is shown
that there exists a threshold on the storage overhead, below
which such an opportunistic approach does not lose any efficiency
from the optimal storage-repair-bandwidth tradeoff; i.e. it is
possible to construct a code simultaneously optimal for different
numbers of helper nodes. We further examine the benefits of such
opportunistic codes, and derive the MTTDL improvement for
two repair models: one with limited total repair bandwidth and
the other with limited individual-node repair bandwidth. In both
settings, we show orders of magnitude improvement in MTTDL.
Finally, the proposed framework is examined in a network setting
where a significant improvement in MTTDL is observed.}},
	att_authors={va037f, ct9807, vv9482, yc2591},
	att_copyright_notice={{This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in 2014. {{, 2014-04-27}}
	author={Vaneet Aggarwal and Chao Tian and Vinay Vaishampayan and Yih-farn Chen},
	institution={{IEEE Infocomm 2014}},
	title={{Distributed Data Storage Systems with Opportunistic Repair}},