| <!DOCTYPE html> |
| <html lang="en"> |
| <head> |
| <meta charset="utf-8"> |
| <meta name="viewport" content="width=device-width,initial-scale=1.0"> |
| <title>Leveled Compaction Strategy | Apache Cassandra Documentation</title> |
| <link rel="stylesheet" href="../../../../../assets/css/site.css"> |
| <link rel="schema.dcterms" href="https://purl.org/dc/terms/"> |
| <meta name="dcterms.subject" content="Cassandra"> |
| <meta name="dcterms.identifier" content="3.11"> |
| <meta name="generator" content="Antora 2.3.4"> |
| <link rel="icon" href="../../../../../assets/img/favicon.ico" type="image/x-icon"> |
| <script> |
| const script = document.createElement("script"); |
| const domain = window.location.hostname; |
| script.type = "text/javascript"; |
| script.src = "https://plausible.cassandra.apache.org/js/plausible.js"; |
| script.setAttribute("data-domain",domain); |
| script.setAttribute("defer",'true'); |
| script.setAttribute("async",'true'); |
| document.getElementsByTagName("head")[0].appendChild(script); |
| </script> </head> |
| <body class="docs-wrapper article"> |
| <div class="container mx-auto relative"> |
| <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script> |
| <meta property="og:type" content="website" /> |
| <meta property="og:url" content="/" /> |
| <meta property="og:site_name" content="Apache Cassandra" /> |
| |
| <header id="top-nav"> |
| <div class="inner relative"> |
| <div class="header-social-icons text-right"> |
| <a href="https://twitter.com/cassandra?lang=en" target="_blank" styles="margin-left: 20px;"><img src="../../../../../assets/img/twitter-icon-circle-white.svg" alt="twitter icon" width="24"></a> |
| <a href="https://www.linkedin.com/company/apache-cassandra/" target="_blank" styles="margin-left: 20px;"><img src="../../../../../assets/img/LI-In-Bug.png" alt="linked-in icon" width="24"></a> |
| <a href="https://www.youtube.com/c/PlanetCassandra" target="_blank" styles="margin-left: 20px;"><img src="../../../../../assets/img/youtube-icon.png" alt="youtube icon" width="24"></a> |
| </div> |
| <div class="cf"> |
| <div class="logo left"><a href="/"><img src="../../../../../assets/img/logo-white-r.png" alt="Cassandra Logo"></a></div> |
| <div class="mobile-nav-icon right"> |
| <img class="toggle-icon" src="../../../../../assets/img/hamburger-nav.svg"> |
| </div> |
| <ul class="main-nav nav-links right flex flex-vert-center flex-space-between"> |
| <li> |
| <a class="nav-link hide-mobile">Get Started</a> |
| <ul class="sub-menu bg-white"> |
| <li class="pa-micro"> |
| <a href="/_/cassandra-basics.html"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-basics.png" alt="cassandra basics icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Cassandra Basics |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro"> |
| <a href="/_/quickstart.html"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-rocket.png" alt="cassandra basics icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Quickstart |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro"> |
| <a href="/_/ecosystem.html"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-ecosystem.png" alt="cassandra basics icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Ecosystem |
| </div> |
| </a> |
| </li> |
| </ul> |
| </li> |
| <li><a class="nav-link" href="/doc/latest/">Documentation</a></li> |
| <li> |
| <a class="nav-link" href="/_/community.html">Community</a> |
| <ul class="sub-menu bg-white"> |
| <li class="pa-micro"> |
| <a href="/_/community.html#code-of-conduct"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-welcome.png" alt="welcome icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Welcome |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro hide-mobile"> |
| <a href="/_/community.html#discussions"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-discussions.png" alt="discussions icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Discussions |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro hide-mobile"> |
| <a href="/_/community.html#project-governance"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-governance.png" alt="Governance icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Governance |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro hide-mobile"> |
| <a href="/_/community.html#how-to-contribute"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-contribute.png" alt="Contribute icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Contribute |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro hide-mobile"> |
| <a href="/_/community.html#meet-the-community"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-community.png" alt="Meet the Community icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Meet the Community |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro hide-mobile"> |
| <a href="/_/cassandra-catalyst-program.html"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-catalyst.png" alt="Catalyst icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Catalyst Program |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro hide-mobile"> |
| <a href="/_/events.html"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-events.png" alt="Events icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Events |
| </div> |
| </a> |
| </li> |
| </ul> |
| </li> |
| <li> |
| <a class="nav-link hide-mobile">Learn</a> |
| <ul class="sub-menu bg-white"> |
| <li class="pa-micro"> |
| <a href="/_/Apache-Cassandra-5.0-Moving-Toward-an-AI-Driven-Future.html"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-basics.png" alt="Basics icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Cassandra 5.0 |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro"> |
| <a href="/_/case-studies.html"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-case-study.png" alt="Case Studies icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Case Studies |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro"> |
| <a href="/_/resources.html"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-resources.png" alt="Resources icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Resources |
| </div> |
| </a> |
| </li> |
| <li class="pa-micro"> |
| <a href="/_/blog.html"> |
| <div class="sub-nav-icon"> |
| <img src="../../../../../assets/img/sub-menu-blog.png" alt="Blog icon"> |
| </div> |
| <div class="sub-nav-text teal py-small"> |
| Blog |
| </div> |
| </a> |
| </li> |
| </ul> |
| </li> |
| <li><a class="nav-link btn btn--filled" href="/_/download.html">Download Now</a></li> |
| </ul> |
| </div> |
| </div> |
| </header> |
| |
| <div class="hero hero--home grad"> |
| <div class="eye"></div> |
| <div id="docs-content" class="text-center flex flex-center flex-column relative z2 ma-xlarge"> |
| <h2>Cassandra Documentation</h2> |
| </div> |
| </div> |
| <div class="body px-medium py-medium container"> |
| <div class="docs-nav-bar flex flex-space-between mb-medium"> |
| <div id="mobile-docs-nav-burger" class="hidden"> |
| <svg viewBox="0 0 24 24" width="36" height="36" stroke="#1c81a0" stroke-width="2.5" fill="none" stroke-linecap="round" stroke-linejoin="round" class="css-i6dzq1"><line x1="3" y1="12" x2="21" y2="12"></line><line x1="3" y1="6" x2="21" y2="6"></line><line x1="3" y1="18" x2="21" y2="18"></line></svg> |
| </div> |
| <div class="docs-nav-item relative"> |
| <input id="search-input" type="text" placeholder="Search docs"> |
| </div> |
| <div class="versions-wrapper"> |
| <h4>Version:</h4> |
| <div class="nav-panel-explore" data-panel="explore"> |
| |
| <div id="version-toggle" class="context"> |
| <span class="version">3.11</span> |
| </div> |
| <ul id="versions-list" class="components"> |
| <li class="component"> |
| <ul class="versions"> |
| <li class="version is-latest"> |
| <a href="../../../../../_/index.html">master</a> |
| </li> |
| </ul> |
| </li> |
| <li class="component is-current"> |
| <ul class="versions"> |
| <li class="version"> |
| <a href="../../../../trunk/index.html">trunk</a> |
| </li> |
| <li class="version"> |
| <a href="../../../../5.0/index.html">5.0</a> |
| </li> |
| <li class="version is-latest"> |
| <a href="../../../../4.1/index.html">4.1</a> |
| </li> |
| <li class="version"> |
| <a href="../../../../4.0/index.html">4.0</a> |
| </li> |
| <li class="version is-current"> |
| <a href="../../../index.html">3.11</a> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </div> |
| </div> </div> |
| <div class="cf relative"> |
| <nav class="nav docs-nav full-800"> |
| <div class="nav-menu"> |
| <ul class="nav-list"> |
| <li class="nav-item is-active" data-depth="0"> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="1"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <a class="nav-link" href="../../../index.html">Main</a> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/glossary.html">Glossary</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/bugs.html">How to report bugs</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/contactus.html">Contact us</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| <li class="nav-item is-active" data-depth="0"> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="1"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <span class="nav-text">Cassandra</span> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <a class="nav-link" href="../../getting_started/index.html">Getting Started</a> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../getting_started/installing.html">Installing Cassandra</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../getting_started/configuring.html">Configuring Cassandra</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../getting_started/querying.html">Inserting and querying</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../getting_started/drivers.html">Client drivers</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../getting_started/production.html">Production recommendations</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <a class="nav-link" href="../../architecture/index.html">Architecture</a> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../architecture/overview.html">Overview</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../architecture/dynamo.html">Dynamo</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../architecture/storage_engine.html">Storage engine</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../architecture/guarantees.html">Guarantees</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <a class="nav-link" href="../../data_modeling/index.html">Data modeling</a> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../data_modeling/intro.html">Introduction</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../data_modeling/data_modeling_conceptual.html">Conceptual data modeling</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../data_modeling/data_modeling_rdbms.html">RDBMS design</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../data_modeling/data_modeling_queries.html">Defining application queries</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../data_modeling/data_modeling_logical.html">Logical data modeling</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../data_modeling/data_modeling_physical.html">Physical data modeling</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../data_modeling/data_modeling_refining.html">Evaluating and refining data models</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../data_modeling/data_modeling_schema.html">Defining database schema</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../data_modeling/data_modeling_tools.html">Cassandra data modeling tools</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <a class="nav-link" href="../../cql/index.html">Cassandra Query Language (CQL)</a> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/definitions.html">Definitions</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/types.html">Data types</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/ddl.html">Data definition (DDL)</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/dml.html">Data manipulation (DML)</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/operators.html">Operators</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/indexes.html">Secondary indexes</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/mvs.html">Materialized views</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/functions.html">Functions</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/json.html">JSON</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/security.html">Security</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/triggers.html">Triggers</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/appendices.html">Appendices</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/changes.html">Changes</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/SASI.html">SASI</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../cql/cql_singlefile.html">Single file of CQL information</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <a class="nav-link" href="../../configuration/index.html">Configuration</a> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../configuration/cass_yaml_file.html">cassandra.yaml</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../configuration/cass_rackdc_file.html">cassandra-rackdc.properties</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../configuration/cass_env_sh_file.html">cassandra-env.sh</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../configuration/cass_topo_file.html">cassandra-topologies.properties</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../configuration/cass_cl_archive_file.html">commitlog-archiving.properties</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../configuration/cass_logback_xml_file.html">logback.xml</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../configuration/cass_jvm_options_file.html">jvm-* files</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <a class="nav-link" href="../index.html">Operating</a> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="#operating/snitch.adoc">Snitches</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../topo_changes.html">Topology changes</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../repair.html">Repair</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../hints.html">Hints</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../bloom_filters.html">Bloom filters</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../compression.html">Compression</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../cdc.html">Change Data Capture (CDC)</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../backups.html">Backups</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../bulk_loading.html">Bulk loading</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../metrics.html">Metrics</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../security.html">Security</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../hardware.html">Hardware</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../audit_logging.html">Audit logging</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="index.html">Compaction</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <a class="nav-link" href="../../tools/index.html">Tools</a> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../tools/cqlsh.html">cqlsh: the CQL shell</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../tools/nodetool/nodetool.html">nodetool</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../tools/sstable/index.html">SSTable tools</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../tools/cassandra_stress.html">cassandra-stress</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <a class="nav-link" href="../../troubleshooting/index.html">Troubleshooting</a> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../troubleshooting/finding_nodes.html">Finding misbehaving nodes</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../troubleshooting/reading_logs.html">Reading Cassandra logs</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../troubleshooting/use_nodetool.html">Using nodetool</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../troubleshooting/use_tools.html">Using external tools to deep-dive</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <button class="nav-toggle"></button> |
| <a class="nav-link" href="../../../../../_/development/index.html">Development</a> |
| </span> |
| <ul class="nav-list"> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/gettingstarted.html">Getting started</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/ide.html">Building and IDE integration</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/testing.html">Testing</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/patches.html">Contributing code changes</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/code_style.html">Code style</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/how_to_review.html">Review checklist</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/how_to_commit.html">How to commit</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/documentation.html">Working on documentation</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/ci.html">Jenkins CI environment</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/dependencies.html">Dependency management</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="3"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../../../../_/development/release_process.html">Release process</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../faq/index.html">FAQ</a> |
| </span> |
| </li> |
| <li class="nav-item" data-depth="2"> |
| <span class="nav-line"> |
| <a class="nav-link" href="../../plugins/index.html">Plug-ins</a> |
| </span> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </div> |
| </nav> |
| <aside class="toc sidebar"> |
| <div class="toc-menu"></div> |
| </aside> |
| <main class="article default-main full-800" data-ceiling="topbar"> |
| <div class="article-banner"> |
| <p>A newer version of this documentation is available.</p> |
| <a class="btn" href="../../../../4.1/cassandra/operating/compaction/lcs.html">View Latest</a> |
| </div> |
| <div class="article-header"> |
| <nav class="crumbs" aria-label="breadcrumbs"> |
| <ul> |
| <li class="crumb"><a href="../../../index.html">Cassandra</a></li> |
| <li class="crumb"><a href="lcs.html">Leveled Compaction Strategy</a></li> |
| </ul> |
| </nav> |
| <div class="tools" role="navigation"> |
| <ul> |
| <li class="tool edit"><a href="file:///home/jenkins/working/cassandra/doc/modules/cassandra/pages/operating/compaction/lcs.adoc" title="Edit Page" target="_blank" rel="noopener">Edit</a></li> |
| </ul> |
| </div> |
| </div> |
| <article class="doc"> |
| <h1 class="page">Leveled Compaction Strategy</h1> |
| <div id="preamble"> |
| <div class="sectionbody"> |
| <div id="lcs" class="paragraph"> |
| <p>The idea of <code>LeveledCompactionStrategy</code> (LCS) is that all sstables are |
| put into different levels where we guarantee that no overlapping |
| sstables are in the same level. By overlapping we mean that the |
| first/last token of a single sstable are never overlapping with other |
| sstables. This means that for a SELECT we will only have to look for the |
| partition key in a single sstable per level. Each level is 10x the size |
| of the previous one and each sstable is 160MB by default. L0 is where |
| sstables are streamed/flushed - no overlap guarantees are given here.</p> |
| </div> |
| <div class="paragraph"> |
| <p>When picking compaction candidates we have to make sure that the |
| compaction does not create overlap in the target level. This is done by |
| always including all overlapping sstables in the next level. For example |
| if we select an sstable in L3, we need to guarantee that we pick all |
| overlapping sstables in L4 and make sure that no currently ongoing |
| compactions will create overlap if we start that compaction. We can |
| start many parallel compactions in a level if we guarantee that we wont |
| create overlap. For L0 → L1 compactions we almost always need to |
| include all L1 sstables since most L0 sstables cover the full range. We |
| also can’t compact all L0 sstables with all L1 sstables in a single |
| compaction since that can use too much memory.</p> |
| </div> |
| <div class="paragraph"> |
| <p>When deciding which level to compact LCS checks the higher levels first |
| (with LCS, a "higher" level is one with a higher number, L0 being the |
| lowest one) and if the level is behind a compaction will be started in |
| that level.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="major-compaction"><a class="anchor" href="#major-compaction"></a><a class="link" href="#major-compaction">Major compaction</a></h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>It is possible to do a major compaction with LCS - it will currently |
| start by filling out L1 and then once L1 is full, it continues with L2 |
| etc. This is sub optimal and will change to create all the sstables in a |
| high level instead, CASSANDRA-11817.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="bootstrapping"><a class="anchor" href="#bootstrapping"></a><a class="link" href="#bootstrapping">Bootstrapping</a></h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>During bootstrap sstables are streamed from other nodes. The level of |
| the remote sstable is kept to avoid many compactions after the bootstrap |
| is done. During bootstrap the new node also takes writes while it is |
| streaming the data from a remote node - these writes are flushed to L0 |
| like all other writes and to avoid those sstables blocking the remote |
| sstables from going to the correct level, we only do STCS in L0 until |
| the bootstrap is done.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="stcs-in-l0"><a class="anchor" href="#stcs-in-l0"></a><a class="link" href="#stcs-in-l0">STCS in L0</a></h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>If LCS gets very many L0 sstables reads are going to hit all (or most) |
| of the L0 sstables since they are likely to be overlapping. To more |
| quickly remedy this LCS does STCS compactions in L0 if there are more |
| than 32 sstables there. This should improve read performance more |
| quickly compared to letting LCS do its L0 → L1 compactions. If you keep |
| getting too many sstables in L0 it is likely that LCS is not the best |
| fit for your workload and STCS could work out better.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="starved-sstables"><a class="anchor" href="#starved-sstables"></a><a class="link" href="#starved-sstables">Starved sstables</a></h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>If a node ends up with a leveling where there are a few very high level |
| sstables that are not getting compacted they might make it impossible |
| for lower levels to drop tombstones etc. For example, if there are |
| sstables in L6 but there is only enough data to actually get a L4 on the |
| node the left over sstables in L6 will get starved and not compacted. |
| This can happen if a user changes sstable_size_in_mb from 5MB to 160MB |
| for example. To avoid this LCS tries to include those starved high level |
| sstables in other compactions if there has been 25 compaction rounds |
| where the highest level has not been involved.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect1"> |
| <h2 id="lcs_options"><a class="anchor" href="#lcs_options"></a><a class="link" href="#lcs_options">LCS options</a></h2> |
| <div class="sectionbody"> |
| <div class="dlist"> |
| <dl> |
| <dt class="hdlist1"><code>sstable_size_in_mb</code> (default: 160MB)</dt> |
| <dd> |
| <p>The target compressed (if using compression) sstable size - the |
| sstables can end up being larger if there are very large partitions on |
| the node.</p> |
| </dd> |
| <dt class="hdlist1"><code>fanout_size</code> (default: 10)</dt> |
| <dd> |
| <p>The target size of levels increases by this fanout_size multiplier. |
| You can reduce the space amplification by tuning this option.</p> |
| </dd> |
| </dl> |
| </div> |
| <div class="paragraph"> |
| <p>LCS also support the <code>cassandra.disable_stcs_in_l0</code> startup option |
| (<code>-Dcassandra.disable_stcs_in_l0=true</code>) to avoid doing STCS in L0.</p> |
| </div> |
| </div> |
| </div> |
| </article> |
| </main> |
| </div> |
| </div> |
| <footer class="grad grad--two flex-center pb-xlarge"> |
| <div class="inner text-center z2 relative"> |
| <h2 class="white py-small">Get started with Cassandra, fast.</h2> |
| <a id="footer-cta" href="/_/quickstart.html" class="btn btn--filled ma-medium">Quickstart Guide</a> |
| </div> |
| <div class="inner flex flex-distribute-items mt-xlarge z2 relative"> |
| <div class="col-2"> |
| <div id="footer-logo" class="logo logo--footer mb-medium"><img src="../../../../../assets/img/logo-white-r.png" alt="Cassandra Logo"></div> |
| <p>Apache Cassandra<img src="../../../../../assets/img/registered.svg" alt="®" style="width:18px;"> powers mission-critical deployments with improved performance and unparalleled levels of scale in the cloud.</p> |
| <div class="footer-social-icons"> |
| <a href="https://twitter.com/cassandra?lang=en" target="_blank"><img src="../../../../../assets/img/twitter-icon-circle-white.svg" alt="twitter icon" width="24"></a> |
| <a href="https://www.linkedin.com/company/apache-cassandra/" target="_blank"><img src="../../../../../assets/img/LI-In-Bug.png" alt="linked-in icon" width="24"></a> |
| <a href="https://www.youtube.com/c/PlanetCassandra" target="_blank"><img src="../../../../../assets/img/youtube-icon.png" alt="youtube icon" width="24"></a> |
| </div> |
| </div> |
| <div class="col-2 flex flex-center"> |
| <ul class="columns-2"> |
| <li class="mb-small"><a href="/">Home</a></li> |
| <li class="mb-small"><a href="/_/cassandra-basics.html">Cassandra Basics</a></li> |
| <li class="mb-small"><a href="/_/quickstart.html">Quickstart</a></li> |
| <li class="mb-small"><a href="/_/ecosystem.html">Ecosystem</a></li> |
| <li class="mb-small"><a href="/doc/latest/">Documentation</a></li> |
| <li class="mb-small"><a href="/_/community.html">Community</a></li> |
| <li class="mb-small"><a href="/_/case-studies.html">Case Studies</a></li> |
| <li class="mb-small"><a href="/_/resources.html">Resources</a></li> |
| <li class="mb-small"><a href="/_/blog.html">Blog</a></li> |
| </ul> |
| </div> |
| </div> |
| </footer> |
| <div class="lower-footer bg-white pa-medium"> |
| <div class="flex flex-row flex-vert-center"> |
| <div class="pr-medium"><img src="../../../../../assets/img//feather-small.png" alt="ASF" width="20"></div> |
| <div class="pr-medium"><a href="http://www.apache.org/" target="_blank">Foundation</a></div> |
| <div class="pr-medium"><a href="https://www.apache.org/events/current-event.html" target="_blank">Events</a></div> |
| <div class="pr-medium"><a href="https://www.apache.org/licenses/" target="_blank">License</a></div> |
| <div class="pr-medium"><a href="https://www.apache.org/foundation/thanks" target="_blank">Thanks</a></div> |
| <div class="pr-medium"><a href="https://www.apache.org/security" target="_blank">Security</a></div> |
| <div class="pr-medium"><a href="https://privacy.apache.org/policies/privacy-policy-public.html" target="_blank">Privacy</a></div> |
| <div class="pr-medium"><a href="https://www.apache.org/foundation/sponsorship" target="_blank">Sponsorship</a></div> |
| </div> |
| <p class="my-medium">© 2009-<script>document.write(new Date().getFullYear())</script> <a href="https://apache.org" target="_blank">The Apache Software Foundation</a> under the terms of the Apache License 2.0. Apache, the Apache feather logo, Apache Cassandra, Cassandra, and the Cassandra logo, are either registered trademarks or trademarks of The Apache Software Foundation.</p> |
| </div> |
| <div id="fade" class="hidden"></div> |
| <div id="modal" class="hidden"> |
| <div id="close-modal" class="cursor-pointer"><svg viewBox="0 0 24 24" width="24" height="24" stroke="currentColor" stroke-width="2" fill="none" stroke-linecap="round" stroke-linejoin="round" class="css-i6dzq1"><line x1="18" y1="6" x2="6" y2="18"></line><line x1="6" y1="6" x2="18" y2="18"></line></svg></div> |
| <div id="mod-content" class="vid-mod-content resp-container"></div> |
| </div> |
| <script src="../../../../../assets/js/site.js"></script> |
| <script async src="../../../../../assets/js/vendor/highlight.js"></script> |
| <script src="../../../../../assets/js/vendor/lunr.js"></script> |
| <script src="../../../../../assets/js/vendor/search.js" id="search-script" data-base-path="../../../../.." data-page-path="/Cassandra/3.11/cassandra/operating/compaction/lcs.html"></script> |
| <script async src="../../../../../assets/../search-index.js"></script> |
| <script> |
| jQuery(function(){ |
| var windowW = $(window).width(); |
| $(document) |
| .on('click','.mobile-nav-icon',function(){ |
| $('.main-nav').fadeIn(); |
| }) |
| .on('click','.main-nav',function(){ |
| if(windowW <= 1000){ |
| $(this).fadeOut(); |
| } |
| }) |
| .on('click','#version-toggle',function(){ |
| $(this).toggleClass('active'); |
| $(this).next().fadeToggle(); |
| }) |
| .on('click','#mobile-docs-nav-burger', function(){ |
| $(this).toggleClass('active'); |
| $('.docs-nav').toggleClass('active'); |
| }); |
| var url = window.location.pathname; |
| var isQuickstart = url.includes('quickstart.html'); |
| if(isQuickstart){ |
| var footerCTA = document.getElementById('footer-cta'); |
| footerCTA.innerHTML = 'Get latest updates'; |
| footerCTA.setAttribute('href', '/_/blog.html'); |
| } |
| }); |
| </script> |
| </div> |
| </body> |
| </html> |
