Abstract-This paper presents ZHT, a zero-hop distributed hash table, which has been tuned for the requirements of high-end computing systems. ZHT aims to be a building block for future distributed systems, such as parallel and distributed file systems, distributed job management systems, and parallel programming systems. The goals of ZHT are delivering high availability, good fault tolerance, high throughput, and low latencies, at extreme scales of millions of nodes. ZHT has some important properties, such as being light-weight, dynamically allowing nodes join and leave, fault tolerant through replication, persistent, scalable, and supporting unconventional operations such as append (providing lock-free concurrent key/value modifications) in addition to insert/lookup/remove. We have evaluated ZHT's performance under a variety of systems, ranging from a Linux cluster with 512-cores, to an IBM Blue Gene/P supercomputer with 160K-cores. Using micro-benchmarks, we scaled ZHT up to 32K-cores with latencies of only 1.1ms and 18M operations/sec throughput. This work provides three real systems that have integrated with ZHT, and evaluate them at modest scales. 1) ZHT was used in the FusionFS distributed file system to deliver distributed meta-data management at over 60K operations (e.g. file create) per second at 2K-core scales. 2) ZHT was used in the IStore, an information dispersal algorithm enabled distributed object storage system, to manage chunk locations, delivering more than 500 chunks/sec at 32-nodes scales. 3) ZHT was also used as a building block to MATRIX, a distributed job scheduling system, delivering 5000 jobs/sec throughputs at 2K-core scales. We compared ZHT against other distributed hash tables and key/value stores and found it offers superior performance for the features and portability it supports.

Abstract-The Advanced Networking Initiative (ANI) project from the Energy Services Network provides a 100 Gbps testbed, which offers the opportunity for evaluating applications and middleware used by scientific experiments. This testbed is a prototype of a 100 Gbps wide-area network backbone, which links several Department of Energy (DOE) national laboratories, universities and other research institutions. These scientific experiments involve movement of large datasets for collaborations among researchers at different sites and thus require advanced infrastructure for supporting large and fast data transfers. A 100 Gbps network testbed is a key component of the ANI project and is used for DOE's science research programs. This work presents results towards obtaining maximum throughput in large data transfers by optimizing and fine-tuning scientific applications and middleware to use this advanced infrastructure efficiently. A detailed performance evaluation is discussed measuring both applications, from High Energy Physics (HEP) and from data transfer middleware (GridFTP, Globus Online, Storage Resource Management, XrootD and Squid) at 100 Gbps speeds and 53 ms of latency. Results show that up to 97% efficiency of such high bandwidth high latency network is possible, achieving 80-90 Gbps in most test cases with a peak transfer rate of 100 Gbps.

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