3,200 research outputs found
Non-homogeneous Two-Rack Model for Distributed Storage Systems
In the traditional two-rack distributed storage system (DSS) model, due to
the assumption that the storage capacity of each node is the same, the minimum
bandwidth regenerating (MBR) point becomes infeasible. In this paper, we design
a new non-homogeneous two-rack model by proposing a generalization of the
threshold function used to compute the tradeoff curve. We prove that by having
the nodes in the rack with higher regenerating bandwidth stores more
information, all the points on the tradeoff curve, including the MBR point,
become feasible. Finally, we show how the non-homogeneous two-rack model
outperforms the traditional model in the tradeoff curve between the storage per
node and the repair bandwidth.Comment: ISIT 2013. arXiv admin note: text overlap with arXiv:1004.0785 by
other author
Increasing Availability in Distributed Storage Systems via Clustering
We introduce the Fixed Cluster Repair System (FCRS) as a novel architecture
for Distributed Storage Systems (DSS), achieving a small repair bandwidth while
guaranteeing a high availability. Specifically we partition the set of servers
in a DSS into clusters and allow a failed server to choose any cluster
other than its own as its repair group. Thereby, we guarantee an availability
of . We characterize the repair bandwidth vs. storage trade-off for the
FCRS under functional repair and show that the minimum repair bandwidth can be
improved by an asymptotic multiplicative factor of compared to the state
of the art coding techniques that guarantee the same availability. We further
introduce Cubic Codes designed to minimize the repair bandwidth of the FCRS
under the exact repair model. We prove an asymptotic multiplicative improvement
of in the minimum repair bandwidth compared to the existing exact repair
coding techniques that achieve the same availability. We show that Cubic Codes
are information-theoretically optimal for the FCRS with and complete
clusters. Furthermore, under the repair-by-transfer model, Cubic Codes are
optimal irrespective of the number of clusters
Distributed Storage in Mobile Wireless Networks with Device-to-Device Communication
We consider the use of distributed storage (DS) to reduce the communication
cost of content delivery in wireless networks. Content is stored (cached) in a
number of mobile devices using an erasure correcting code. Users retrieve
content from other devices using device-to-device communication or from the
base station (BS), at the expense of higher communication cost. We address the
repair problem when a device storing data leaves the cell. We introduce a
repair scheduling where repair is performed periodically and derive analytical
expressions for the overall communication cost of content download and data
repair as a function of the repair interval. The derived expressions are then
used to evaluate the communication cost entailed by DS using several erasure
correcting codes. Our results show that DS can reduce the communication cost
with respect to the case where content is downloaded only from the BS, provided
that repairs are performed frequently enough. If devices storing content arrive
to the cell, the communication cost using DS is further reduced and, for large
enough arrival rate, it is always beneficial. Interestingly, we show that MDS
codes, which do not perform well for classical DS, can yield a low overall
communication cost in wireless DS.Comment: After final editing for publication in TCO
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