<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="6.x">Drupal-Biblio</source-app><ref-type>47</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fábio Coelho</style></author><author><style face="normal" font="default" size="100%">Francisco Cruz</style></author><author><style face="normal" font="default" size="100%">Ricardo Vilaça</style></author><author><style face="normal" font="default" size="100%">José Orlando Pereira</style></author><author><style face="normal" font="default" size="100%">Rui Oliveira</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">pH1: A Transactional Middleware for NoSQL</style></title><secondary-title><style face="normal" font="default" size="100%">33rd IEEE International Symposium on Reliable Distributed Systems - SRDS</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2014</style></year><pub-dates><date><style  face="normal" font="default" size="100%">October</style></date></pub-dates></dates><urls><related-urls><url><style face="normal" font="default" size="100%">https://haslab.uminho.pt/sites/default/files/facoelho/files/ph1.pdf</style></url></related-urls></urls><pub-location><style face="normal" font="default" size="100%">Nara, Japan</style></pub-location><abstract><style face="normal" font="default" size="100%">&lt;p&gt;NoSQL databases opt not to offer important abstractions traditionally found in relational databases in order to achieve high levels of scalability and availability: transactional guarantees and strong data consistency.&lt;br /&gt;
In this work we propose pH1, a generic middleware layer over NoSQL databases that offers transactional guarantees with Snapshot Isolation. This is achieved in a non-intrusive manner,&lt;br /&gt;
requiring no modifications to servers and no native support for multiple versions. Instead, the transactional context is achieved by means of a multiversion distributed cache and an external&lt;br /&gt;
transaction certifier, exposed by extending the client’s interface with transaction bracketing primitives.&lt;br /&gt;
We validate and evaluate pH1 with Apache Cassandra and Hyperdex. First, using the YCSB benchmark, we show that the cost of providing ACID guarantees to these NoSQL databases&lt;br /&gt;
amounts to 11% decrease in throughput.&lt;br /&gt;
Moreover, using the transaction intensive TPC-C workload, pH1 presented an impact of 22% decrease in throughput. This contrasts with OMID, a previous proposal that takes advantage of&lt;br /&gt;
HBase’s support for multiple versions, with a throughput penalty of 76% in the same conditions.&lt;/p&gt;
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