My research interests include High-Performance Interconnects and Protocols (e.g., RDMA), Erasure Coding, In-Network Computing, and Distributed Systems.
Erasure coding (EC) is a promising fault tolerance scheme that has been applied to many well-known distributed storage systems. The capability of Coherent EC Calculation and Networking on modern SmartNICs has demonstrated that EC will be an essential feature of in-network computing. In this paper, we propose a set of coherent in-network EC primitives, named INEC. Our analyses based on the proposed α-β performance model demonstrate that INEC primitives can enable different kinds of EC schemes to fully leverage the EC offload capability on modern SmartNICs. We implement INEC on commodity RDMA NICs and integrate it into five state-of-the-art EC schemes. Our experiments show that INEC primitives significantly reduce 50th, 95th, and 99th percentile latencies, and accelerate the end-to-end throughput, write, and degraded read performance of the key-value store co-designed with INEC by up to 99.57%, 47.30%, and 49.55%, respectively.
Erasure Coding (EC) NIC offload is a promising technology for designing next-generation distributed storage systems. However, this paper has identified three major limitations of current-generation EC NIC offload schemes on modern SmartNICs. Thus, this paper proposes a new EC NIC offload paradigm based on the tripartite graph model, namely TriEC. TriEC supports both encode-and-send and receive-and-decode operations efficiently. Through theorem-based proofs, co-designs with memcached (i.e., TriEC-Cache), and extensive experiments, we show that TriEC is correct and can deliver better performance than the state-of-the-art EC NIC offload schemes (i.e., BiEC). Benchmark evaluations demonstrate that TriEC outperforms BiEC by up to 1.82x and 2.33x for encoding and recovering, respectively. With extended YCSB workloads, TriEC reduces the average write latency by up to 23.2% and the recovery time by up to 37.8%. TriEC outperforms BiEC by 1.32x for a full-node recovery with 8 million records.
Distributed storage systems typically need data to be stored redundantly to guarantee data durability and reliability. While the conventional approach towards this objective is to store multiple replicas, today's unprecedented data growth rates encourage modern distributed storage systems to employ Erasure Coding (EC) techniques, which can achieve better storage efficiency. Various hardware-based EC schemes have been proposed in the community to leverage the advanced compute capabilities on modern data center and cloud environments. Currently, there is no unified and easy way for distributed storage systems to fully exploit multiple devices such as CPUs, GPUs, and network devices (i.e., multi-rail support) to perform EC operations in parallel; thus, leading to the under-utilization of the available compute power. In this paper, we first introduce an analytical model to analyze the design scope of efficient EC schemes in distributed storage systems. Guided by the performance model, we propose UMR-EC, a Unified and Multi-Rail Erasure Coding library that can fully exploit heterogeneous EC coders. Our proposed interface is complemented by asynchronous semantics with optimized metadata-free scheme and EC rate-aware task scheduling that can enable a highly-efficient I/O pipeline. To show the benefits and effectiveness of UMR-EC, we re-design HDFS 3.x write/read pipelines based on the guidelines observed in the proposed performance model. Our performance evaluations show that our proposed designs can outperform the write performance of replication schemes and the default HDFS EC coder by 3.7x - 6.1x and 2.4x - 3.3x, respectively, and can improve the performance of read with failure recoveries up to 5.1x compared with the default HDFS EC coder. Compared with the fastest available CPU coder (i.e., ISA-L), our proposed designs have an improvement of up to 66.0% and 19.4% for write and read with failure recoveries, respectively.
Various Erasure Coding (EC) schemes based on hardware accelerations have been proposed in the community to leverage the advanced compute capabilities on modern data centers, such as Intel ISA-L Onload EC coders and Mellanox InfiniBand Offload EC coders. These EC coders can play a vital role in designing next-generation distributed storage systems. Unfortunately, there does not exist a unified and easy way for distributed storage systems researchers and designers to benchmark, measure, and characterize the performance of these different EC coders. In this context, we propose a unified benchmark suite, called EC-Bench, to help the users to benchmark both onload and offload EC coders on modern hardware architectures. EC-Bench provides both encoding and decoding benchmarks with tunable parameter support. A rich set of metrics, including latency, actual and normalized throughput, CPU utilization, and cache pressure, can be reported through EC-Bench. Evaluations with EC-Bench demonstrate that hardware-optimized offload coders (e.g. Mellanox-EC) have lower demands on CPU and cache compared to onload coders, and highly optimized onload coders (e.g., Intel ISA-L) outperform offload coders for most configurations.
Efficient Big Data analytics on Cloud Computing systems is still full of challenges. One of the biggest hurdles is the unsatisfactory performance offered by underlying virtualized I/O devices such as networks. To address this issue, the modern cloud resource providers (e.g., Microsoft Azure) have deployed high-performance networks, such as Remote Direct Memory Access (RDMA) capable networks in their clouds. However, in this paper, we find that by far, the RDMA networks on Microsoft Azure cannot support either IPoIB or native standard Verbs-based RDMA protocols. Instead, applications need to use the uDAPL (i.e., user Direct Access Programming Library) interface to enable RDMA communication on Azure Cloud, which makes impossible for modern Big Data stacks to leverage these high-performance networks as none of them can support the uDAPL interface yet. To address this issue, we first design an efficient uDAPL-based communication library with the best combinations of uDAPL communication operations. Then, we adapt the designed uDAPL library into the Hadoop RPC ping-pong message passing engine and the Spark Shuffle engine for bulk data transferring. Through our designs, we can improve the performance of Big Data analytics workloads with Hadoop RPC and Spark on RDMA-enabled Azure VMs by up to 90% and 82%, respectively, and save users' cloud resource renting cost by 4.24x. To the best of our knowledge, this is the first work to design a uDAPL-based RDMA communication engine for Big Data analytics stacks (e.g., Spark).
Deep Learning over Big Data (DLoBD) is an emerging paradigm to mine value from the massive amount of gathered data. Many Deep Learning frameworks, like Caffe, TensorFlow, etc., start running over Big Data stacks, such as Apache Hadoop and Spark. Even though a lot of activities are happening in the field, there is a lack of comprehensive studies on analyzing the impact of RDMA-capable networks and CPUs/GPUs on DLoBD stacks. To fill this gap, we propose a systematical characterization methodology and conduct extensive performance evaluations on four representative DLoBD stacks (i.e., CaffeOnSpark, TensorFlowOnSpark, MMLSpark/CNTKOnSpark, and BigDL) to expose the interesting trends regarding performance, scalability, accuracy, and resource utilization. Our observations show that RDMA-based design for DLoBD stacks can achieve up to 2.7x speedup compared to the IPoIB-based scheme. The RDMA scheme also scales better and utilizes resources more efficiently than IPoIB. For most cases, GPU-based schemes can outperform CPU-based designs, but we see that for LeNet on MNIST, CPU + MKL can achieve better performance than GPU and GPU + cuDNN on 16 nodes. Through our evaluation and an in-depth analysis on TensorFlowOnSpark, we find that there are large rooms to improve the designs of current-generation DLoBD stacks.
IBM's POWER processor has been advocated as the high-performance architecture designed for processing Big Data workloads. With the collaborations through the OpenPOWER Foundation, more and more innovations for POWER architecture are emerging to solve Big Data challenges. For example, with the cooperation between IBM and Mellanox, the latest generation of Remote Direct Memory Access (RDMA) capable InfiniBand network can deliver tremendous performance on POWER processors. On the other hand, many RDMA-based designs and optimizations recently have been proposed in the community for accelerating big data processing systems (such as Apache Hadoop and Spark). However, these studies mostly focus on achieving higher performance over Intel Xeon or other x86 architectures. As OpenPOWER systems are getting momentum, we set out to answer the question how much can the RDMA-based communication runtime benefit Big Data processing middleware running over OpenPOWER systems as compared to the default TCP/IP-based designs. To answer this question, this paper first presents an extensive performance characterization on RDMA-based Hadoop RPC engine over OpenPOWER system. We further propose new designs to enable efficient CPU affinity policies and architecture-aware tuning in the RDMA-based communication engine for Hadoop and Spark. With these various accelerations, our performance evaluation shows that our proposed designs can achieve up to 2.73X performance improvement for Hadoop RPC benchmark as compared to default Hadoop running with IP-over-IB protocol on OpenPOWER systems. In addition, our proposed design can gain up to 29.37% performance improvement for Hadoop and Spark workloads as compared to the default RDMA designs running on an OpenPOWER cluster.
Deep Learning over Big Data (DLoBD) is becoming one of the most important research paradigms to mine value from the massive amount of gathered data. Many emerging deep learning frameworks start running over Big Data stacks, such as Hadoop and Spark. With the convergence of HPC, Big Data, and Deep Learning, these DLoBD stacks are taking advantage of RDMA and multi-/many-core based CPUs/GPUs. Even though a lot of activities are happening in the field, there is a lack of systematic studies on analyzing the impact of RDMA-capable networks and CPU/GPU on DLoBD stacks. To fill this gap, we propose a systematical characterization methodology and conduct extensive performance evaluations on three representative DLoBD stacks (i.e., CaffeOnSpark, TensorFlowOnSpark, and BigDL) to expose the interesting trends regarding performance, scalability, accuracy, and resource utilization. Our observations show that RDMA-based design for DLoBD stacks can achieve up to 2.7x speedup compared to the IPoIB based scheme. The RDMA scheme can also scale better and utilize resources more efficiently than the IPoIB scheme over InfiniBand clusters. For most cases, GPU-based deep learning can outperform CPU-based designs, but not always. We see that for LeNet on MNIST, CPU + MKL can achieve better performance than GPU and GPU + cuDNN on 16 nodes. Through our evaluation, we see that there are large rooms to improve the designs of current generation DLoBD stacks further.