Hypervisor-based virtualization technology has been successfully used to deploy high-performance and scalable infrastructure for Hadoop, and now Spark applications. Container-based virtualization techniques are becoming an important option, which is increasingly used due to their lightweight operation and better scaling when compared to Virtual Machines (VM). With containerization techniques such as Docker becoming mature and promising better performance, we can use Docker to speed-up big data applications. However, as applications have different behaviors and resource requirements, before replacing traditional hypervisor-based virtual machines with Docker, it is important to analyze and compare performance of applications running in the cloud with VMs and Docker containers. VM provides distributed resource management for different virtual machines running with their own allocated resources, while Docker relies on shared pool of resources among all containers. Here, we investigate the performance of different Apache Spark applications using both Virtual Machines (VM) and Docker containers. While others have looked at Docker's performance, this is the first study that compares these different virtualization frameworks for a big data enterprise cloud environment using Apache Spark. In addition to makespan and execution time, we also analyze different resource utilization (CPU, disk, memory, etc.) by Spark applications. Our results show that Spark using Docker can obtain speed-up of over 10 times when compared to using VM. However, we observe that this may not apply to all applications due to different workload patterns and different resource management schemes performed by virtual machines and containers. Our work can guide application developers, system administrators and researchers to better design and deploy big data applications on their platforms to improve the overall performance.

In the year of 2017, the capital expenditure of Flash-based Solid State Drivers (SSDs) keeps declining and the storage capacity of SSDs keeps increasing. As a result, the “selling point” of traditional spinning Hard Disk Drives (HDDs) as a backend storage - low cost and large capacity - is no longer unique, and eventually they will be replaced by low-end SSDs which have large capacity but perform orders of magnitude better than HDDs. Thus, it is widely believed that all-flash multi-tier storage systems will be adopted in the enterprise datacenters in the near future. However, existing caching or tiering solutions for SSD-HDD hybrid storage systems are not suitable for all-flash storage systems. This is because that all-flash storage systems do not have a large speed difference (e.g., 10×) among each tier. Instead, different specialties (such as high performance, high capacity, etc.) of each tier should be taken into consideration. Motivated by this, we develop an automatic data placement manager called “AutoTiering” to handle virtual machine disk files (VMDK) allocation and migration in an all-flash multitier datacenter to best utilize the storage resource, optimize the performance, and reduce the migration overhead. AutoTiering is based on an optimization framework, whose core technique is to predict VM's performance change on different tiers with different specialties without conducting real migration. As far as we know, AutoTiering is the first optimization solution designed for all-flash multi-tier datacenters. We implement AutoTiering on VMware ESXi [1], and experimental results show that it can significantly improve the I/O performance compared to existing solutions.

We propose a nearby traffic flow modelling solution based on built-in Cyber-Physical System (CPS) sensors of autonomous vehicles. Our goal is to enhance the offline route planning and driving decision adjustment based on the first-hand traffic information, especially during poor Internet connection moments. Specifically, our model helps to select the optimal speed on a road, the optimal distance for timing to brake, and the safe distance from other vehicles to keep. Moreover, our model can also assist neighboring autonomous vehicles by communicating required information through Ad-Hoc network communications or through a centralized cloud. In detail, we first focus on the unique characteristic of traffic flow (such as traffic rule, avoid collision behaviours), and then build a comprehensive model to handle multiple scenarios. Technically, our model uses density functions of velocities, the differential equation of traffic flows, and the traffic viscosity with information collected from the traffic flow, the distances between vehicles, the amount and density of vehicle, the instant velocity, the speed limit, and the momentum to analysis the the driving scene. We evaluate our model with real traffic data collected by in-vehicle CPS sensors to the proposed nearby traffic flow model. Results show that our work can accurately conduct offline estimation on nearby traffic signal influence, and reveal the correlations among velocity, density and (spatial and temporal) location to adjust route during runtime.

Nowadays, replication technique is widely used in data center storage systems for large scale Cyber-physical Systems (CPS) to prevent data loss. However, side-effect of replication is mainly the overhead of extra network and I/O traffics, which inevitably downgrades the overall I/O performance of the cluster. To effectively balance the trade-off between I/O performance and fault tolerance, in this paper, we propose a complete solution called “AutoReplica” - a replica manager in distributed caching and data processing systems with SSD-HDD tier storages. In detail, AutoReplica utilizes the remote SSDs (connected by high speed fibers) to replicate local SSD caches to protect data. In order to conduct load balancing among nodes and reduce the network overhead, we propose three approaches (i.e., ring, network, and multiple-SLA network) to automatically setup the cross-node replica structure with the consideration of network traffic, I/O speed and SLAs. To improve the performance during migrations triggered by load balance and failure recovery, we propose the a migrate-on-write technique called “fusion cache” to seamlessly migrate and prefetch among local and remote replicas without pausing the subsystem. Moreover, AutoReplica can also recover from different failure scenarios, while limits the performance downgrading degree. Lastly, AutoReplica supports parallel prefetching from multiple nodes with a new dynamic optimizing streaming technique to improve I/O performance. We are currently in the process of implementing AutoReplica to be easily plugged into commonly used distributed caching systems, and solidifying our design and implementation details.

Our cloud-based IT world is founded on hyper-visors and containers. Containers are becoming an important cornerstone, which is increasingly used day-by-day. Among different available frameworks, docker has become one of the major adoptees to use containerized platform in data centers and enterprise servers, due to its ease of deploying and scaling. Further more, the performance benefits of a lightweight container platform can be leveraged even more with a fast back-end storage like high performance SSDs. However, increase in number of simultaneously operating docker containers may not guarantee an aggregated performance improvement due to saturation. Thus, understanding performance bottleneck in a multi-tenancy docker environment is critically important to maintain application level fairness and perform better resource management. In this paper, we characterize the performance of persistent storage option (through data volume) for I/O intensive, dockerized applications. Our work investigates the impact on performance with increasing number of simultaneous docker containers in different workload environments. We provide, first of its kind study of I/O intensive containerized applications operating with NVMe SSDs. We show that 1) a six times better application throughput can be obtained, just by wise selection of number of containerized instances compared to single instance; and 2) for multiple application containers running simultaneously, an application throughput may degrade upto 50% compared to a stand-alone applications throughput, if good choice of application and workload is not made. We then propose novel design guidelines for an optimal and fair operation of both homogeneous and heterogeneous environments mixed with different applications and workloads.

Due to the flexibility of data operations and scalability of in- memory cache, Spark has revealed the potential to become the standard distributed framework to replace Hadoop for data-intensive processing in both industry and academia. However, we observe that the built-in scheduling algorithms in Spark (i.e., FIFO and FAIR) are not optimized for the applications with multiple parallel and independent branches in stages. Specifically, the child stage needs to wait and collect data from all its parent branches, but this wait has no guaranteed upper bound since it is tightly coupled with each branch's workload characteristic, stage order, and their corresponding allocated computing resource. To address this challenge, we investigate a superior solution which ensures all branches acquire suitable resources according to their workload demand in order to let the finish time of each branch be as close as possible. Based on this, we propose a novel scheduling policy, named AutoPath, which can effectively reduce the overall makespan of such kind of applications by detecting and leveraging the parallel path, and adaptively assigning computing resources based on the estimated workload demands during runtime. We implemented the new scheduling scheme in Spark v1.5.0 and evaluated it with selected representative workloads. The experiments demonstrate that our new scheduler effectively reduces the makespan and improves resource utilizations for these applications, compared to the current FIFO and FAIR schedulers.