The RAMCloud Storage System Ousterhout, John; Gopalan, Arjun; Gupta, Ashish ...
ACM transactions on computer systems,
09/2015, Letnik:
33, Številka:
3
Journal Article
Recenzirano
Odprti dostop
RAMCloud is a storage system that provides low-latency access to large-scale datasets. To achieve low latency, RAMCloud stores all data in DRAM at all times. To support large capacities (1PB or ...more), it aggregates the memories of thousands of servers into a single coherent key-value store. RAMCloud ensures the durability of DRAM-based data by keeping backup copies on secondary storage. It uses a uniform log-structured mechanism to manage both DRAM and secondary storage, which results in high performance and efficient memory usage. RAMCloud uses a polling-based approach to communication, bypassing the kernel to communicate directly with NICs; with this approach, client applications can read small objects from any RAMCloud storage server in less than 5μs, durable writes of small objects take about 13.5μs. RAMCloud does not keep multiple copies of data online; instead, it provides high availability by recovering from crashes very quickly (1 to 2 seconds). RAMCloud’s crash recovery mechanism harnesses the resources of the entire cluster working concurrently so that recovery performance scales with cluster size.
Distributed consensus is fundamental to building fault-tolerant systems. It allows a collection of machines to work as a coherent group that can survive the failures of some of its members. ...Unfortunately, the most common consensus algorithm, , is widely regarded as difficult to understand and implement correctly. This dissertation presents a new consensus algorithm called Raft, which was designed for understandability. Raft first elects a server as leader, then concentrates all decision-making onto the leader. These two basic steps are relatively independent and form a better structure than Paxos, whose components are hard to separate. Raft elects a leader using voting and randomized timeouts. The election guarantees that the leader already stores all the information it needs, so data only flows outwards from the leader to other servers. Compared to other leader-based algorithms, this reduces mechanism and simplifies the behavior. Once a leader is elected, it manages a replicated log. Raft leverages a simple invariant on how logs grow to reduce the algorithm's state space and accomplish this task with minimal mechanism. Raft is also more suitable than previous algorithms for real-world implementations. It performs well enough for practical deployments, and it addresses all aspects of building a complete system, including how to manage client interactions, how to change the cluster membership, and how to compact the log when it grows too large. To change the cluster membership, Raft allows adding or removing one server at a time (complex changes can be composed from these basic steps), and the cluster continues servicing requests throughout the change. We believe that Raft is superior to Paxos and other consensus algorithms, both for educational purposes and as a foundation for implementation. Results from a user study demonstrate that Raft is easier for students to learn than Paxos. The algorithm has been formally specified and proven, its leader election algorithm works well in a variety of environments, and its performance is equivalent to Multi-Paxos. Many implementations of Raft are now available, and several companies are deploying Raft.
Fast crash recovery in RAMCloud Ongaro, Diego; Rumble, Stephen M.; Stutsman, Ryan ...
Proceedings of the Twenty-Third ACM Symposium on Operating Systems Principles,
10/2011
Conference Proceeding
Odprti dostop
RAMCloud is a DRAM-based storage system that provides inexpensive durability and availability by recovering quickly after crashes, rather than storing replicas in DRAM. RAMCloud scatters backup data ...across hundreds or thousands of disks, and it harnesses hundreds of servers in parallel to reconstruct lost data. The system uses a log-structured approach for all its data, in DRAM as well as on disk: this provides high performance both during normal operation and during recovery. RAMCloud employs randomized techniques to manage the system in a scalable and decentralized fashion. In a 60-node cluster, RAMCloud recovers 35 GB of data from a failed server in 1.6 seconds. Our measurements suggest that the approach will scale to recover larger memory sizes (64 GB or more) in less time with larger clusters.
Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-09-28T17:29:12Z;
No. of bitstreams: 1;
diegobaratazanottiongaro.pdf: 2707234 bytes, checksum: cb7b623f86bc2a312c703ccbc541a7b3 (MD5)
Approved ...for entry into archive by Diamantino Mayra (mayra.diamantino@ufjf.edu.br) on 2016-09-30T13:38:46Z (GMT) No. of bitstreams: 1;
diegobaratazanottiongaro.pdf: 2707234 bytes, checksum: cb7b623f86bc2a312c703ccbc541a7b3 (MD5)
Made available in DSpace on 2016-09-30T13:38:46Z (GMT). No. of bitstreams: 1;
diegobaratazanottiongaro.pdf: 2707234 bytes, checksum: cb7b623f86bc2a312c703ccbc541a7b3 (MD5);
Previous issue date: 2016-04-11
O cinema, como ação de um transitar político no mundo, estampa nos nossos próprios corpos os efeitos de uma intensa mobilidade contemporânea. Mas o que, de fato, move o cinema? Sendo uma prática de espaços, o filme cria o seu próprio itinerário de passagem cuja emoção é o seu principal afeto de transporte - imagens e sujeitos mobilizam e são mobilizados pelo filme. Pautados nesse cinema de afetos, nos aliamos ao trabalho da diretora mineira Clarissa Campolina, a partir dos filmes O Porto, Trecho e Girimunho. Com eles propomos um itinerário especial em torno de questões sobre os espaços esvaziados pelo poder hegemônico, sobre o deslocamento errante e a força de um “movimento menor”. Reflexões que trazem à tona o deslocar como potência, como performance de trânsito nos espaços da tela e da vida que não cessam de apresentar novas configurações e conteúdos, que nos convidam a reconhecer as geopoéticas que redesenham, a todo momento, a nossa própria travessia no mundo.
The cinema, as the action of a political transition in the world, pattern in our own bodies the effects of an intense contemporary mobility. But what, in fact, move the movies? As a practice of spaces, the cinema creates itself its own passage itinerary whose emotion is its main transport affection - images and subjects mobilize and are mobilized by the film. Guided by this cinema of affects, we have allied ourselves with the work of the Brazilian director Clarissa Campolina, with the movies Porto, Trecho and Girimunho. With them, we propose a special itinerary aimed to specific questions relating to space emptied by the hegemonic power, the errant displacement and the strength of a "minor movement". Reflections that bring out the displacement as a potency, as a traffic performance in the areas of the screen and life that are constantly presenting new settings and contents, which invite us to recognize the geopoetics that redraw, all the time, our own world journey.
The case for RAMCloud Ousterhout, John; Agrawal, Parag; Erickson, David ...
Communications of the ACM,
07/2011, Letnik:
54, Številka:
7
Magazine Article
With scalable high-performance storage entirely in DRAM, RAMCloud will enable a new breed of data-intensive applications.
The Case for RAMCloud Ousterhout, John; Agrawal, Parag; Erickson, David ...
Communications of the ACM,
07/2011, Letnik:
54, Številka:
7
Magazine Article
For the past four decades magnetic disks have been the primary storage location for online information in computer systems. However, disk performance has not improved as quickly as disk capacity, and ...developers find it increasingly difficult to scale disk-based systems to meet the needs of large-scale Web applications. A new class of storage called RAMCloud will provide the storage substrate for many future applications. RAMCloud stores all of its information in the main memories of commodity servers and uses hundreds or thousands of these servers to create a large-scale storage system.
Surgery is the only curative treatment for non-metastatic pancreatic adenocarcinoma, but less than 20 % of patients present a resectable disease at diagnosis. Treatment strategies and disease ...definition for borderline resectable pancreatic cancer (BRPC) and locally advanced pancreatic cancer (LAPC) vary in the different cancer centres. Preoperative chemotherapy (CT) is the standard of care for both BRPC and LAPC patients, however literature data are still controversial concerning the type, dose and duration of the different CT regimens, as well as regarding the integration of radiotherapy (RT) or chemoradiation (CRT) in the therapeutic algorithm. In this unsettled debate, we aimed at focusing on the therapeutic regimens currently in use and relative literature data, to report international trials comparing the available therapeutic options or explore the introduction of new pharmacological agents, and to analyse possible new scenarios in microenvironment evaluation before and after neoadjuvant therapies or in patients’ selection at a molecular level.
Display omitted
•Less than 20 % of pancreatic cancer patients have a resectable disease at diagnosis.•BRPC and LAPC patients need a preoperative treatment, including CT and possibly RT.•Treatment algorithms are still debated and vary in the different cancer centres.•New therapeutic options and microenvironment-targeted agents are being evaluated.•Consultation at high-volume centres and inclusion in clinical trials are advisable.
Human sirtuins are seven proteins with deacetylase activity that are emerging as key modulators of basic physiological functions. Some evidence links SIRT3 to longevity in mammals. This study aimed ...to investigate whether variants within
SIRT3
gene were associated to human longevity. We analyzed 549 genomic DNA collected during the prospective study “Treviso Longeva,” including elderly over 70 years of age from the municipality of Treviso, a small city in the northeast of Italy. We genotyped
SIRT3
rs3825075, rs4980329, and rs11555236 single nucleotide polymorphisms (SNPs) by real-time polymerase chain reaction allelic discrimination assay. A cross-sectional analysis performed by comparing people over and under 85 years of age did not evidence association among the
SIRT3
SNPs and longevity. However, when we performed a longitudinal analysis considering mortality as a dependent variable, we observed an association of
SIRT3
rs11555236 and rs4980329 with longevity in the whole population (
p
values corrected for potential confounders = 0.04 and 0.03, respectively). After stratification according to gender, the same SNPs were associated to female longevity only (
p
values corrected for potential confounders = 0.03 and 0.02, respectively). Finally, as rs11555236 was reported to be in linkage disequilibrium with a putative functional enhancer within the
SIRT3
gene, we assessed whether rs11555236 genotypes correlated with a different level of SIRT3 protein in peripheral blood mononuclear cells. We found an increased level of SIRT3 in subjects homozygous for the (T) allele. We suggest that
SIRT3
genetic variability might be relevant for the modulation of human longevity in the Italian population.
The article studies the dynamics of fiscal consolidation and public sector reforms in Italy and Spain under the EU governance that took shape as a reaction to the Eurozone crisis. We show how three ...types of EU pressure - fiscal and economic coordination rules, conditionality, and back-room diplomacy have operated in conjunction. We also show that Italy was more willing than Spain to resist EU pressure. Based on a Two-Level Game framework, we argue that this can be explained by the greater opposition to European integration that has developed in Italy compared to Spain.
PDF
