15 research outputs found
A Class of MSR Codes for Clustered Distributed Storage
Clustered distributed storage models real data centers where intra- and
cross-cluster repair bandwidths are different. In this paper, exact-repair
minimum-storage-regenerating (MSR) codes achieving capacity of clustered
distributed storage are designed. Focus is given on two cases: and
, where is the ratio of the available cross- and
intra-cluster repair bandwidths, is the total number of distributed nodes
and is the number of contact nodes in data retrieval. The former represents
the scenario where cross-cluster communication is not allowed, while the latter
corresponds to the case of minimum cross-cluster bandwidth that is possible
under the minimum storage overhead constraint. For the case, two
types of locally repairable codes are proven to achieve the MSR point. As for
, an explicit MSR coding scheme is suggested for the
two-cluster situation under the specific condition of .Comment: 9 pages, a part of this paper is submitted to IEEE ISIT201
Explicit Construction of Minimum Bandwidth Rack-Aware Regenerating Codes
In large data centers, storage nodes are organized in racks, and the
cross-rack communication dominates the system bandwidth. We explicitly
construct codes for exact repair of single node failures that achieve the
optimal tradeoff between the storage redundancy and cross-rack repair bandwidth
at the minimum bandwidth point (i.e., the cross-rack bandwidth equals the
storage size per node). Moreover, we explore the node repair when only a few
number of helper racks are connected. Thus we provide explicit constructions of
codes for rack-aware storage with the minimum cross-rack repair bandwidth,
lowest possible redundancy, and small repair degree (i.e., the number of helper
racks connected for repair).Comment: 4 pages, 1 figure. arXiv admin note: text overlap with
arXiv:2101.0873
Global repair bandwidth cost optimization of generalized regenerating codes in clustered distributed storage systems
In clustered distributed storage systems (CDSSs), one of the main design goals is minimizing the transmission cost during the failed storage nodes repairing. Generalized regenerating codes (GRCs) are proposed to balance the intra-cluster repair bandwidth and the inter-cluster repair bandwidth for guaranteeing data availability. The trade-off performance of GRCs illustrates that, it can reduce storage overhead and inter-cluster repair bandwidths simultaneously. However, in practical big data storage scenarios, GRCs cannot give an effective solution to handle the heterogeneity of bandwidth costs among different clusters for node failures recovery. This paper proposes an asymmetric bandwidth allocation strategy (ABAS) of GRCs for the inter-cluster repair in heterogeneous CDSSs. Furthermore, an upper bound of the achievable capacity of ABAS is derived based on the information flow graph (IFG), and the constraints of storage capacity and intra-cluster repair bandwidth are also elaborated. Then, a metric termed global repair bandwidth cost (GRBC), which can be minimized regarding of the inter-cluster repair bandwidths by solving a linear programming problem, is defined. The numerical results demonstrate that, maintaining the same data availability and storage overhead, the proposed ABAS of GRCs can effectively reduce the GRBC compared to the traditional symmetric bandwidth allocation schemes
Node repair on connected graphs, Part II
We continue our study of regenerating codes in distributed storage systems
where connections between the nodes are constrained by a graph. In this
problem, the failed node downloads the information stored at a subset of
vertices of the graph for the purpose of recovering the lost data. This
information is moved across the network, and the cost of node repair is
determined by the graphical distance from the helper nodes to the failed node.
This problem was formulated in our recent work (IEEE IT Transactions, May 2022)
where we showed that processing of the information at the intermediate nodes
can yield savings in repair bandwidth over the direct forwarding of the data.
While the previous paper was limited to the MSR case, here we extend our
study to the case of general regenerating codes. We derive a lower bound on the
repair bandwidth and formulate repair procedures with intermediate processing
for several families of regenerating codes, with an emphasis on the recent
constructions from multilinear algebra. We also consider the task of data
retrieval for codes on graphs, deriving a lower bound on the communication
bandwidth and showing that it can be attained at the MBR point of the
storage-bandwidth tradeoff curve
Rack-aware minimum-storage regenerating codes with optimal access
We derive a lower bound on the amount of information accessed to repair
failed nodes within a single rack from any number of helper racks in the
rack-aware storage model that allows collective information processing in the
nodes that share the same rack. Furthermore, we construct a family of
rack-aware minimum-storage regenerating (MSR) codes with the property that the
number of symbols accessed for repairing a single failed node attains the bound
with equality for all admissible parameters. Constructions of rack-aware
optimal-access MSR codes were only known for limited parameters. We also
present a family of Reed-Solomon (RS) codes that only require accessing a
relatively small number of symbols to repair multiple failed nodes in a single
rack. In particular, for certain code parameters, the RS construction attains
the bound on the access complexity with equality and thus has optimal access