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Date: Tue, 26 Nov 1996 00:22:08 GMTServer: NCSA/1.4.2Content-type: text/htmlLast-modified: Wed, 12 Jul 1995 21:57:26 GMTContent-length: 3143<html><head><title>eNVy</title> </head><body><h1>eNVy</h1> <hr><p> eNVy is a design for a large solid state storage system builtprimarily with Flash memory. Its main goal is to provide extremelyfast and reliable access to persistent data. The obvious applicationsthat can benefit from such a system are databases since their performanceis usually bound by the time it takes to retrieve and modify data.While all databases can obtain significant benefits when using eNVy,object oriented databases are especially well suited since the fastaccess time of solid state storage effectively eliminates the penaltiescaused by difficulties in optimizing for sequential disk access incurrent systems.<p> In the eNVy storage system data is stored permanently in solid-state(Flash) memory, asopposed to traditional systems where data is stored on disk and readsare sped up by a volatile DRAM cache. Flash technology's inherentnon-volatility allows eNVy to serve as a permanent data repositoryrather than a volatile cache. Flash's simple structure offers a costadvantageover all other forms of solid-state memory. While this still doesn'tallow Flash to compete with magnetic disks in terms of cost per bit in the near future, it does provide a solid state storage alternativethat can be used for performance enhancement when disks are too slow.<p> eNVy differs from other Flash products in that its storage is memory mapped. Memory mapping allows much more efficient fine grainedaccess than a disk interface but is made difficult by three basicproblems with Flash memory, inability to update in-place, relativelylarge write latencies, and limited erasure cycling. eNVy overcomesthe update problem by using page mapping to implement a copy-on-writescheme with a small amount of battery-backed SRAM to make updates appearto be done in-place even though they actually are not. The copy-on-writefunction also almost entirely hides the Flash write latency. Wide bussesprovide high performance and an efficient cleaning algorithm that includeswear-leveling maximizes the life of the Flash array. In effect, eNVy provides a solid state storage system similar inboth image and performance to a large array of memory mapped, battery backedSRAM but at a greatly reduced cost. Our simulations show that a typical 2 gigabyte store can support I/O rates corresponding to approximately30,000 transactions per second on the TPC-A database benchmark.Average read and write latencies for the simulations were 180ns forreads and 200ns for writes.<p><hr><h2> eNVy Papers </h2><li> <!WA0><a href="http://www.cs.rice.edu/CS/Systems/papers/envy-asplos94.ps.gz">"eNVy, A Non-Volatile, Main Memory Storage System", M. Wu and W. Zwaenepoel,Proceedings of the 6th Symposium on Architectural Support for Programming Languages and Operating Systems, pp. 86-97, October 1994.</a><p><li> <!WA1><a href="http://www.cs.rice.edu/CS/Systems/papers/envy-techrpt.ps.gz">"The Architecture of eNVy, A Non-Volatile, Main Memory Storage System",M. Wu, Rice Computer Science Tech Report #94-299, April, 1994.</a><p>⌨️ 快捷键说明
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