ramcloud - Appears in SIGOPS Operating Systems Review, Vol....

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Appears in SIGOPS Operating Systems Review , Vol. 43, No. 4, December 2009, pp. 92-105 The Case for RAMClouds: Scalable High-Performance Storage Entirely in DRAM John Ousterhout, Parag Agrawal, David Erickson, Christos Kozyrakis, Jacob Leverich, David Mazières, Subhasish Mitra, Aravind Narayanan, Guru Parulkar, Mendel Rosenblum, Stephen M. Rumble, Eric Stratmann, and Ryan Stutsman Department of Computer Science Stanford University Abstract Disk-oriented approaches to online storage are becoming increasingly problematic: they do not scale grace- fully to meet the needs of large-scale Web applications, and improvements in disk capacity have far out- stripped improvements in access latency and bandwidth. This paper argues for a new approach to datacenter storage called RAMCloud, where information is kept entirely in DRAM and large-scale systems are created by aggregating the main memories of thousands of commodity servers. We believe that RAMClouds can provide durable and available storage with 100-1000x the throughput of disk-based systems and 100-1000x lower access latency. The combination of low latency and large scale will enable a new breed of data- intensive applications. 1 Introduction For four decades magnetic disks have provided the primary means of storing online information in com- puter systems. Over that period disk technology has undergone dramatic improvements, and it has been harnessed by a variety of higher-level storage systems such as file systems and relational databases. However, the performance of disk has not improved as rapidly as its capacity, and developers are finding it increasingly difficult to scale disk-based systems to meet the needs of large-scale Web applications. Many people have proposed new approaches to disk-based storage as a solution to this problem; others have suggested replac- ing disks with flash memory devices. In contrast, we believe that the solution is to shift the primary locus of online data from disk to random access memory, with disk relegated to a backup/archival role. In this paper we argue that a new class of storage called RAMCloud will provide the storage substrate for many future applications. A RAMCloud stores all of its in- formation in the main memories of commodity servers, using hundreds or thousands of such servers to create a large-scale storage system. Because all data is in DRAM at all times, a RAMCloud can provide 100- 1000x lower latency than disk-based systems and 100- 1000x greater throughput. Although the individual memories are volatile, a RAMCloud can use replication and backup techniques to provide data durability and availability equivalent to disk-based systems. We believe that RAMClouds will fundamentally change the storage landscape in three ways. First, they will simplify the development of large-scale Web ap- plications by eliminating many of the scalability issues that sap developer productivity today. Second, their extremely low latency will enable richer query models
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ramcloud - Appears in SIGOPS Operating Systems Review, Vol....

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