2,677 research outputs found
Cooperative Regenerating Codes for Distributed Storage Systems
When there are multiple node failures in a distributed storage system,
regenerating the failed storage nodes individually in a one-by-one manner is
suboptimal as far as repair-bandwidth minimization is concerned. If data
exchange among the newcomers is enabled, we can get a better tradeoff between
repair bandwidth and the storage per node. An explicit and optimal construction
of cooperative regenerating code is illustrated.Comment: 5 pages, 7 figures, to appear in Proc. IEEE ICC, 201
Distributed Storage Systems based on Equidistant Subspace Codes
Distributed storage systems based on equidistant constant dimension codes are
presented. These equidistant codes are based on the Pl\"{u}cker embedding,
which is essential in the repair and the reconstruction algorithms. These
systems posses several useful properties such as high failure resilience,
minimum bandwidth, low storage, simple algebraic repair and reconstruction
algorithms, good locality, and compatibility with small fields
Self-repairing Homomorphic Codes for Distributed Storage Systems
Erasure codes provide a storage efficient alternative to replication based
redundancy in (networked) storage systems. They however entail high
communication overhead for maintenance, when some of the encoded fragments are
lost and need to be replenished. Such overheads arise from the fundamental need
to recreate (or keep separately) first a copy of the whole object before any
individual encoded fragment can be generated and replenished. There has been
recently intense interest to explore alternatives, most prominent ones being
regenerating codes (RGC) and hierarchical codes (HC). We propose as an
alternative a new family of codes to improve the maintenance process, which we
call self-repairing codes (SRC), with the following salient features: (a)
encoded fragments can be repaired directly from other subsets of encoded
fragments without having to reconstruct first the original data, ensuring that
(b) a fragment is repaired from a fixed number of encoded fragments, the number
depending only on how many encoded blocks are missing and independent of which
specific blocks are missing. These properties allow for not only low
communication overhead to recreate a missing fragment, but also independent
reconstruction of different missing fragments in parallel, possibly in
different parts of the network. We analyze the static resilience of SRCs with
respect to traditional erasure codes, and observe that SRCs incur marginally
larger storage overhead in order to achieve the aforementioned properties. The
salient SRC properties naturally translate to low communication overheads for
reconstruction of lost fragments, and allow reconstruction with lower latency
by facilitating repairs in parallel. These desirable properties make
self-repairing codes a good and practical candidate for networked distributed
storage systems
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
Capacity and Security of Heterogeneous Distributed Storage Systems
We study the capacity of heterogeneous distributed storage systems under
repair dynamics. Examples of these systems include peer-to-peer storage clouds,
wireless, and Internet caching systems. Nodes in a heterogeneous system can
have different storage capacities and different repair bandwidths. We give
lower and upper bounds on the system capacity. These bounds depend on either
the average resources per node, or on a detailed knowledge of the node
characteristics. Moreover, we study the case in which nodes may be compromised
by an eavesdropper, and give bounds on the system secrecy capacity. One
implication of our results is that symmetric repair maximizes the capacity of a
homogeneous system, which justifies the model widely used in the literature.Comment: 7 pages, 2 figure
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