Jipeng Zhou

Adaptive fault-tolerant wormhole routing in 2D meshes

We present an adaptive fault-tolerant wormhole routing algorithm for 2D meshes. The main feature is that with the algorithm, a normal routing message, when blocked by some faulty processes would detour along the f-polygons around the fault region. The proposed algorithm can tolerate convex faults with only three virtual channels per physical channel regardless of the overlapping of f-polygons of different fault regions. The proposed algorithm is deadlock-free.

Architectures and optimization methods of flash memory based storage systems

Flash memory is a non-volatile memory which can be electrically erased and reprogrammed. Its major advantages such as small physical size, no mechanical components, low power consumption, and high performance have made it likely to replace the magnetic disk drives in more and more systems. However, flash memory has four specific features which are different to the magnetic disk drives, and pose challenges to develop practical techniques: (1) Flash memory is erased in blocks, but written in pages. (2) A block has to be erased before writing data to the block. (3) A block of flash memory can only be written for a specified number of times. (4) Writing pages within a block should be done sequentially. This survey presents the architectures, technologies, and optimization methods employed by the existing flash memory based storage systems to tackle the challenges. I hope that this paper will encourage researchers to analyze, optimize, and develop practical techniques to improve the performance and reduce the energy consumption of flash memory based storage systems, by leveraging the existing methods and solutions.

Adaptive fault-tolerant wormhole routing with two virtual channels in 2D meshes

An adaptive fault-tolerant wormhole routing algorithm based on a convex fault model in 2D meshes is presented. With the algorithm, a normal routing message, when blocked by faulty processors, would detour along some special polygons around the fault region. The result is that the proposed algorithm can tolerate convex faults with only two virtual channels per physical channel regardless of the overlapping of the boundaries of different fault regions. The convex fault model used does not include any nonfaulty processors and the proposed algorithm is deadlock-free.

Multi-phase minimal fault-tolerant wormhole routing in meshes

In a multiprocessor system, it is important that the shortest path is always selected for inter-process communication. If every node in the system can acquire the accurate status of all nodes, then optimal routing is possible, but this is not feasible in view of the space and time costs involved. We propose a fault-tolerant wormhole routing algorithm for the mesh network in this paper, which is based on the idea of multi-phase minimal routing. The algorithm requires only local information at every node. When messages in transit come in contact with a fault region, they would select a locally minimal path around the region. The proposed algorithm can tolerate convex fault regions with only four virtual channels per physical channel regardless of how processors of different fault regions may overlap. The aggregation of locally minimal path segments gives a complete routing path between source and destination. Via simulation, we find that the algorithm has near optimal performance in most cases.

Skewly replicating hot data to construct a power-efficient storage cluster

The exponential data growth is presenting challenges to traditional storage systems. Component-based cluster storage systems, due to their high scalability, are becoming the architecture of next generation storage systems. Cluster storage systems often use data replication to ensure high availability, fault tolerance, and load balance. However, this kind of data replication not only consumes a large amount of storage resources, but also generates more energy consumption. This paper presents a power-aware data replication strategy by leveraging data access behavior. This strategy uses 80/20 rule (80% of the data accesses often go to 20% of the storage space) to skewly replicate only a small amount of frequently accessed data. Furthermore, the storage nodes are divided into a hot node set and a cold node set. Hot nodes, which store a small amount of hot data copies, are always in an active state to guarantee the QoS of the system. The cold nodes which store a large volume of infrequently accessed cold data are placed in a low-power state, thus reducing the energy consumption of the cluster storage system. Simulation results show that the proposed strategy can effectively reduce the resource and energy consumption of the system, while ensuring system performance.

Fault-tolerant wormhole routing in 2D meshes

A deterministic fault-tolerant wormhole routing algorithm is presented for mesh networks in this paper. The proposed algorithm can tolerate convex fault-connected regions with only three virtual channels per physical channel, and overlapping of processors along the boundaries of different fault regions is allowed. The proposed algorithm, which routes the messages by XY routing algorithm in the fault-free regions, is deadlock- and livelock-free.

Self-similarity: Behind workload reshaping and prediction

Energy efficiency has become one of the most important challenges in designing future computing systems. Workload reshaping and prediction have a significant impact on the energy conservation of computer components. In this paper, by using three HTTP traffic traces, we perform various evaluations to explore the possible reasons and indications which impact the workload reshaping and prediction. The experimental results indicate that the principles of reshaping workload to improve prediction quality are constructing or improving the self-similarity of the reshaped workloads.

An on-demand routing protocol for improving channel use efficiency in multichannel ad hoc networks

In wireless ad hoc networks, end-to-end delivery over network is a critical concern for routing protocols. The capacity of routing protocols is constrained by the intra-flow interference introduced by adjacent nodes on the same path, and inter-flow interference generated by nodes from neighboring paths. In this paper, we develop an on-demand routing protocol M-AODV-R that solves the channel assignment, reuse and routing problem jointly. The proposed channel reuse scheme and channel assignment scheme can enhance channel reuse rate. This cross-layer design approach can significantly improve the performance of multichannel ad hoc networks over existing routing protocols. Simulation results show that the proposed routing M-AODV-R can effectively increase throughput and reduce delay, as compared to AODV protocol.

Multiphase minimal fault-tolerant wormhole routing in 2D meshes

A fault-tolerant wormhole routing algorithm using multiphase minimal routing paths for mesh networks is proposed in this paper. When routing messages come in contact with a fault region, they always select a local shortest path around the fault-region in clockwise or counter clockwise direction. The proposed algorithm can tolerate convex fault-connected regions with four virtual channels per physical channel regardless of how processors of different f-polygons overlap. The fault regions divide each routing path into multiple minimal routing paths-a multiphase minimal routing path. The performance of multiphase minimal routing vs. minimal routing is compared by simulation.

Efficient online coflow routing and scheduling

A coflow is a collection of related parallel flows that occur typically between two stages of a multi-stage compute task in a network, such as shuffle flows in MapReduce. The coflow abstraction allows applications to convey their semantics to the network so that application-level requirements (e.g., minimizing the completion time of the slowest flow) can be better satisfied. In this paper, we study the routing and scheduling of multiple coflows to minimize the average coflow completion time (CCT). We first propose a rounding-based randomized approximation algorithm, called OneCoflow, for single coflow routing and scheduling. The multiple coflow problem is more challenging as coexisting coflows will compete for the same network resources such as link bandwidths. To minimize the average CCT, we derive an online multiple coflow routing and scheduling algorithm, called OMCoflow, and prove that it has a reasonably good competitive ratio. To the best of our knowledge, this is the first online algorithm with theoretical performance guarantees which considers routing and scheduling simultaneously for multi-coflows. Compared with existing methods, OMCoflow runs more efficiently, and it avoids the problem of frequently rerouting the flows. Extensive simulations on a Facebook data trace show that OMCoflow outperforms the state-of-the-art heuristic schemes significantly (e.g., reducing the average CCT by up to 41.8% and the execution time by up to 99.2% against RAPIER [28]).