Network Traffic Driven Storage Repair

Recently we constructed an explicit family of locally repairable and locally regenerating codes. Their existence was proven by Kamath et al. but no explicit construction was given. Our design is based on HashTag codes that can have different sub-packetization levels. In this work we emphasize the importance of having two ways to repair a node: repair only with local parity nodes or repair with both local and global parity nodes. We say that the repair strategy is network traffic driven since it is in connection with the concrete system and code parameters: the repair bandwidth of the code, the number of I/O operations, the access time for the contacted parts and the size of the stored file. We show the benefits of having repair duality in one practical example implemented in Hadoop. We also give algorithms for efficient repair of the global parity nodes.Comment: arXiv admin note: text overlap with arXiv:1701.0666

Load-Balanced Fractional Repetition Codes

We introduce load-balanced fractional repetition (LBFR) codes, which are a strengthening of fractional repetition (FR) codes. LBFR codes have the additional property that multiple node failures can be sequentially repaired by downloading no more than one block from any other node. This allows for better use of the network, and can additionally reduce the number of disk reads necessary to repair multiple nodes. We characterize LBFR codes in terms of their adjacency graphs, and use this characterization to present explicit constructions LBFR codes with storage capacity comparable existing FR codes. Surprisingly, in some parameter regimes, our constructions of LBFR codes match the parameters of the best constructions of FR codes

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

To repair or not to repair: an investigation of the factors influencing prosumer repair propensity

The Circular Economy is a sustainable system of production and consumption that aims to minimise waste, emissions and energy leakages through a closed system. Repair is one of the strategies to facilitate the transition towards the Circular Economy (CE). Repair is also a behaviour that the prosumer can adopt and enact in collaboration with other citizens in society. The inclination to repair, called explicitly in this thesis, ‘the prosumer’s propensity to repair’ is influenced and affected by a myriad of complex and inter-related elements. Those elements need to be further investigated to support the actors involved in the transition towards the CE to develop interventions to support the prosumer to repair further. The investigation was set in an extreme case scenario by choosing to engage with individuals who, by their affiliation with pro-environmental organisations, appear to be more inclined to engage with pro-environmental behaviours. The investigation focuses on them trying to repair small electrical items because there have been conflicting results in previous research, on the extent to which environmental concerns influence Prosumer Repair Propensity. The literature explores Repair as an activitiy to be embraced by prosumers and strategy to facilitate the transition towards a CE. The review discusses the role, and capacity of the prosumers in to both produce and consume value to support the transition. The literature explores the role of Design in developing solutions to extend product lifespan and to influence prosumer behaviour. The literature in the field of Design for Sustainable Behaviour emphasises the significance of investigating prosumer behaviour before developing interventions. As a result, the literature reviews past research on the factors influencing Prosumer Repair Propensity and behavioural frameworks that could support the investigation. The Theory of Trying and the Transtheoretical model of Change are selected as tools for understanding prosumer repair behaviour as a multi-dimensional object.Two studies are undertaken to meet the research objectives set out for the investigation. Two hundred and eight respondents completed a survey for the Survey study. For the Prosumer study, 10 participants completed a survey, a semi-structured interview and two video-elicitation exercises. The analysis and integration of the findings from the Survey study and Prosumer study helped to consolidate five sets of findings. The first set of findings presents the range of factors influencing Prosumer Repair Propensity; it includes the most significant factors to support the engagement with repair practice and the most critical factors to successfully repair an item. The second set of findings examines the attitudes towards trying to repair. The third set of findings presents the processes of change affecting the prosumer to repair. The fourth and fifth set of findings presents the repair process and considers how the factors and attitudes influence the prosumer at different stages of the repair process. From the findings, suggestions are given on the prosumer actions that can be adopted to support the transition towards the CE. The thesis finally closes on the limitations of the research project and recommends areas for further research to support the prosumer to change.</div