Tag Archives: Servers

Stochastic Modeling and Optimization of Stragglers

Abstract: MapReduce framework is widely used to parallelize batch jobs since it exploits a high degree of multi-tasking to process them. However, it has been observed that when the number of servers increases, the map phase can take much longer than expected. This paper analytically shows that the stochastic behavior of the servers has a negative effect on the completion time of a MapReduce job, and continuously increasing the number of servers without accurate scheduling can degrade the overall performance. We analytically model the map phase in terms of hardware, system, and application parameters to capture the effects of stragglers on the performance. Mean sojourn time (MST), the time needed to sync the completed tasks at a reducer, is introduced as a performance metric and mathematically formulated. Following that, we stochastically investigate the optimal task scheduling which leads to an equilibrium property in a datacenter with different types of servers. Our experimental results show the performance of the different types of schedulers targeting MapReduce applications. We also show that, in the case of mixed deterministic and stochastic schedulers, there is an optimal scheduler that can always achieve the lowest MST.

Authors: Farshid Farhat and Diman Zad Tootaghaj from Penn State, Yuxiong He from MSR (Microsoft Research)

. The work was done during my visit from MSR in Summer 2015.

Stochastic modeling and optimization of stragglers in mapreduce framework

  title={Stochastic modeling and optimization of stragglers in mapreduce framework},
  author={Farhat, Farshid},
  school={The Pennsylvania State University}


Stochastic modeling and optimization of stragglers

  title={Stochastic modeling and optimization of stragglers},
  author={Farhat, Farshid and Tootaghaj, Diman and He, Yuxiong and Sivasubramaniam, Anand and Kandemir, Mahmut and Das, Chita},
  journal={IEEE Transactions on Cloud Computing},

Node Architecture and Cloud Workload Characteristics Analysis

The combined impact of node architecture and workload characteristics on off-chip network traffic with performance/cost analysis has not been investigated before in the context of emerging cloud applications. Motivated by this observation, this paper performs a thorough characterization of twelve cloud workloads using a full-system datacenter simulation infrastructure. We first study the inherent network characteristics of emerging cloud applications including message inter-arrival times, packet sizes, inter-node communication overhead, self-similarity, and traffic volume. Then, we study the effect of hardware architectural metrics on network traffic. Our experimental analysis reveals that (1) the message arrival times and packet-size distributions exhibit variances across different cloud applications, (2) the inter-arrival times imply a large amount of self-similarity as the number of nodes increase, (3) the node architecture can play a significant role in shaping the overall network traffic, and finally, (4) the applications we study can be broadly divided into those which perform better in a scale-out or scale-up configuration at node level and into two categories, namely, those that have long-duration, low-burst flows and those that have short-duration, high-burst flows. Using the results of (3) and (4), the paper discusses the performance/cost trade-offs for scale-out and scale-up approaches and proposes an analytical model that can be used to predict the communication and computation demand for different configurations. It is shown that the difference between two different node architecture’s performance per dollar cost (under same number of cores system wide) can be as high as 154 percent which disclose the need for accurate characterization of cloud applications before wasting the precious cloud resources by allocating wrong architecture. The results of this study can be used for system modeling, capacity planning and managing heterogeneous resources for large-scale system designs.

Full Text > Combined Impact of Node Architecture and Cloud Workload Characteristics

More info > Diman Zad Tootaghaj ‘s Publications