What is RAMCloud?
RAMCloud is a new class of storage for large-scale datacenter applications. It is a key-value store that keeps all data in DRAM at all times (it is not a cache like memcached). Furthermore, it takes advantage of high-speed networking such as Infiniband or 10Gb Ethernet to provide very high performance. Applications running in the same datacenter as a RAMCloud cluster can access small objects in about 5μs, which is1000x faster than disk-based storage systems. Small writes take about 15μs. At the same time, RAMCloud storage is durable: data is automatically replicated on nonvolatile secondary storage such as disk or flash, so it is not lost when servers crash. One of RAMCloud's unique features is that it recovers very quickly from server crashes (only 1-2 seconds) so the availability gaps after crashes are almost unnoticeable. Finally, RAMCloud is designed to scale: it can support clusters containing thousands of storage servers, with total capacities up to a few petabytes.
From a practical standpoint, RAMCloud enables a new class of applications that manipulate large data sets very intensively. Using RAMCloud, an application can combine tens of thousands of items of data in real time to provide instantaneous responses to user requests. Unlike traditional databases, RAMCloud scales to support very large applications, while still providing a high level of consistency. We believe that RAMCloud, or something like it, will become the primary storage system for structured data in cloud computing environments such as Amazon's AWS or Microsoft's Azure. We have built the system not as a research prototype, but as a production-quality software system, suitable for use by real applications.
RAMCloud is also interesting from a research standpoint. Its two most important attributes are latency and scale. The first goal is to provide the lowest possible end-to-end latency for applications accessing the system from within the same datacenter. We currently achieve latencies of around 5μs for reads and 15μs for writes, but hope to improve these in the future. In addition, the system must scale, since no single machine can store enough DRAM to meet the needs of large-scale applications. We have designed RAMCloud to support at least 10,000 storage servers; the system must automatically manage all the information across the servers, so that clients do not need to deal with any distributed systems issues. The combination of latency and scale creates a large number of interesting research issues. To date we have addressed several of these, such as how to ensure data durability without sacrificing the latency of reads and writes, how to take advantage of the scale of the system to recover very quickly after crashes, and how to manage storage in DRAM. Many more issues remain, such as whether we can provide higher-level features such as secondary indexes and multiple-object transactions without sacrificing the latency or scalability of the system. We are currently exploring several of these issues.
The RAMCloud project is based in the Department of Computer Science at Stanford University, but the system is being used at numerous sites around the world.
Learning about RAMCloud
The links below provide general information about RAMCloud, such as talks and papers.
- Introductory talk on RAMCloud by John Ousterhout, given at LinkedIn on October 12, 2011.
- The Case for RAMCloud: an early position paper that discusses the motivation for RAMCloud, the new kinds of applications it may enable, and some of the research issues that will have to be addressed to create a working system. Appeared in CACM in July 2011.
- An earlier and a slightly longer version of the position paper, which appeared in Operating Systems Review in December 2009.
- Fast Recovery in RAMCloud: describes RAMCloud's mechanism for recovering crashed servers in 1-2 seconds. Appeared in SOSP in October, 2011
- It's Time for Low Latency: HotOS 2011 workshop paper arguing for the OS community to focus on network latency.
Articles about RAMCloud (Web and print media, written by people outside the RAMCloud group)
- RAMCloud Presentations (Slides from talks about RAMCloud)
- Glossary of RAMCloud Terms
How to deploy and use RAMCloud
System is already usable
RAMCloud Performance
Information for RAMCloud developers
The RAMCloud test cluster at Stanford
Design notes
Project history and status
Related information
Miscellaneous topics
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What is RAMCloud?
The RAMCloud project is creating a new class of storage, based entirely in DRAM, that is 2-3 orders of magnitude faster than existing storage systems. If successful, it will enable new applications that manipulate large-scale datasets much more intensively than has ever been possible before. In addition, we think RAMCloud, or something like it, will become the primary storage system for cloud computing environments such as Amazon's AWS and Microsoft's Azure.
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