73 research outputs found
High-Rate Regenerating Codes Through Layering
In this paper, we provide explicit constructions for a class of exact-repair
regenerating codes that possess a layered structure. These regenerating codes
correspond to interior points on the storage-repair-bandwidth tradeoff, and
compare very well in comparison to scheme that employs space-sharing between
MSR and MBR codes. For the parameter set with , we
construct a class of codes with an auxiliary parameter , referred to as
canonical codes. With in the range , these codes operate in
the region between the MSR point and the MBR point, and perform significantly
better than the space-sharing line. They only require a field size greater than
. For the case of , canonical codes can also be shown to
achieve an interior point on the line-segment joining the MSR point and the
next point of slope-discontinuity on the storage-repair-bandwidth tradeoff.
Thus we establish the existence of exact-repair codes on a point other than the
MSR and the MBR point on the storage-repair-bandwidth tradeoff. We also
construct layered regenerating codes for general parameter set ,
which we refer to as non-canonical codes. These codes also perform
significantly better than the space-sharing line, though they require a
significantly higher field size. All the codes constructed in this paper are
high-rate, can repair multiple node-failures and do not require any computation
at the helper nodes. We also construct optimal codes with locality in which the
local codes are layered regenerating codes.Comment: 20 pages, 9 figure
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
- …