| |
| |
| <!DOCTYPE html> |
| <!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]--> |
| <!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]--> |
| <head> |
| <meta charset="utf-8"> |
| |
| <meta name="viewport" content="width=device-width, initial-scale=1.0"> |
| |
| <title>Size Tiered Compaction Strategy — Apache Cassandra Documentation v4.0-rc2</title> |
| |
| |
| |
| |
| |
| |
| |
| |
| <script type="text/javascript" src="../../_static/js/modernizr.min.js"></script> |
| |
| |
| <script type="text/javascript" id="documentation_options" data-url_root="../../" src="../../_static/documentation_options.js"></script> |
| <script type="text/javascript" src="../../_static/jquery.js"></script> |
| <script type="text/javascript" src="../../_static/underscore.js"></script> |
| <script type="text/javascript" src="../../_static/doctools.js"></script> |
| <script type="text/javascript" src="../../_static/language_data.js"></script> |
| <script async="async" type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/latest.js?config=TeX-AMS-MML_HTMLorMML"></script> |
| |
| <script type="text/javascript" src="../../_static/js/theme.js"></script> |
| |
| |
| |
| |
| <link rel="stylesheet" href="../../_static/css/theme.css" type="text/css" /> |
| <link rel="stylesheet" href="../../_static/pygments.css" type="text/css" /> |
| <link rel="stylesheet" href="../../_static/extra.css" type="text/css" /> |
| <link rel="index" title="Index" href="../../genindex.html" /> |
| <link rel="search" title="Search" href="../../search.html" /> |
| </head> |
| |
| <body class="wy-body-for-nav"> |
| |
| |
| <div class="wy-grid-for-nav"> |
| |
| <nav data-toggle="wy-nav-shift" class="wy-nav-side"> |
| <div class="wy-side-scroll"> |
| <div class="wy-side-nav-search" > |
| |
| |
| |
| <a href="../../index.html" class="icon icon-home"> Apache Cassandra |
| |
| |
| |
| </a> |
| |
| |
| |
| |
| <div class="version"> |
| 4.0-rc2 |
| </div> |
| |
| |
| |
| |
| <div role="search"> |
| <form id="rtd-search-form" class="wy-form" action="../../search.html" method="get"> |
| <input type="text" name="q" placeholder="Search docs" /> |
| <input type="hidden" name="check_keywords" value="yes" /> |
| <input type="hidden" name="area" value="default" /> |
| </form> |
| </div> |
| |
| |
| </div> |
| |
| <div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation"> |
| |
| |
| |
| |
| |
| |
| <ul> |
| <li class="toctree-l1"><a class="reference internal" href="../../getting_started/index.html">Getting Started</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../new/index.html">New Features in Apache Cassandra 4.0</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../architecture/index.html">Architecture</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../cql/index.html">The Cassandra Query Language (CQL)</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../data_modeling/index.html">Data Modeling</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../configuration/index.html">Configuring Cassandra</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../index.html">Operating Cassandra</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../tools/index.html">Cassandra Tools</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../troubleshooting/index.html">Troubleshooting</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../development/index.html">Contributing to Cassandra</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../faq/index.html">Frequently Asked Questions</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../plugins/index.html">Third-Party Plugins</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../bugs.html">Reporting Bugs</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="../../contactus.html">Contact us</a></li> |
| </ul> |
| |
| |
| |
| </div> |
| </div> |
| </nav> |
| |
| <section data-toggle="wy-nav-shift" class="wy-nav-content-wrap"> |
| |
| |
| <nav class="wy-nav-top" aria-label="top navigation"> |
| |
| <i data-toggle="wy-nav-top" class="fa fa-bars"></i> |
| <a href="../../index.html">Apache Cassandra</a> |
| |
| </nav> |
| |
| |
| <div class="wy-nav-content"> |
| |
| <div class="rst-content"> |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| <div role="navigation" aria-label="breadcrumbs navigation"> |
| |
| <ul class="wy-breadcrumbs"> |
| |
| <li><a href="../../index.html">Docs</a> »</li> |
| |
| <li>Size Tiered Compaction Strategy</li> |
| |
| |
| <li class="wy-breadcrumbs-aside"> |
| |
| |
| <a href="../../_sources/operating/compaction/stcs.rst.txt" rel="nofollow"> View page source</a> |
| |
| |
| </li> |
| |
| </ul> |
| |
| |
| <hr/> |
| </div> |
| <div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article"> |
| <div itemprop="articleBody"> |
| |
| <div class="section" id="size-tiered-compaction-strategy"> |
| <span id="stcs"></span><h1>Size Tiered Compaction Strategy<a class="headerlink" href="#size-tiered-compaction-strategy" title="Permalink to this headline">¶</a></h1> |
| <p>The basic idea of <code class="docutils literal notranslate"><span class="pre">SizeTieredCompactionStrategy</span></code> (STCS) is to merge sstables of approximately the same size. All |
| sstables are put in different buckets depending on their size. An sstable is added to the bucket if size of the sstable |
| is within <code class="docutils literal notranslate"><span class="pre">bucket_low</span></code> and <code class="docutils literal notranslate"><span class="pre">bucket_high</span></code> of the current average size of the sstables already in the bucket. This |
| will create several buckets and the most interesting of those buckets will be compacted. The most interesting one is |
| decided by figuring out which bucket’s sstables takes the most reads.</p> |
| <div class="section" id="major-compaction"> |
| <h2>Major compaction<a class="headerlink" href="#major-compaction" title="Permalink to this headline">¶</a></h2> |
| <p>When running a major compaction with STCS you will end up with two sstables per data directory (one for repaired data |
| and one for unrepaired data). There is also an option (-s) to do a major compaction that splits the output into several |
| sstables. The sizes of the sstables are approximately 50%, 25%, 12.5%… of the total size.</p> |
| </div> |
| <div class="section" id="stcs-options"> |
| <span id="id1"></span><h2>STCS options<a class="headerlink" href="#stcs-options" title="Permalink to this headline">¶</a></h2> |
| <dl class="simple"> |
| <dt><code class="docutils literal notranslate"><span class="pre">min_sstable_size</span></code> (default: 50MB)</dt><dd><p>Sstables smaller than this are put in the same bucket.</p> |
| </dd> |
| <dt><code class="docutils literal notranslate"><span class="pre">bucket_low</span></code> (default: 0.5)</dt><dd><p>How much smaller than the average size of a bucket a sstable should be before not being included in the bucket. That |
| is, if <code class="docutils literal notranslate"><span class="pre">bucket_low</span> <span class="pre">*</span> <span class="pre">avg_bucket_size</span> <span class="pre"><</span> <span class="pre">sstable_size</span></code> (and the <code class="docutils literal notranslate"><span class="pre">bucket_high</span></code> condition holds, see below), then |
| the sstable is added to the bucket.</p> |
| </dd> |
| <dt><code class="docutils literal notranslate"><span class="pre">bucket_high</span></code> (default: 1.5)</dt><dd><p>How much bigger than the average size of a bucket a sstable should be before not being included in the bucket. That |
| is, if <code class="docutils literal notranslate"><span class="pre">sstable_size</span> <span class="pre"><</span> <span class="pre">bucket_high</span> <span class="pre">*</span> <span class="pre">avg_bucket_size</span></code> (and the <code class="docutils literal notranslate"><span class="pre">bucket_low</span></code> condition holds, see above), then |
| the sstable is added to the bucket.</p> |
| </dd> |
| </dl> |
| </div> |
| <div class="section" id="defragmentation"> |
| <h2>Defragmentation<a class="headerlink" href="#defragmentation" title="Permalink to this headline">¶</a></h2> |
| <p>Defragmentation is done when many sstables are touched during a read. The result of the read is put in to the memtable |
| so that the next read will not have to touch as many sstables. This can cause writes on a read-only-cluster.</p> |
| </div> |
| </div> |
| |
| |
| </div> |
| |
| </div> |
| <footer> |
| |
| |
| <hr/> |
| |
| <div role="contentinfo"> |
| <p> |
| © Copyright 2020, The Apache Cassandra team |
| |
| </p> |
| </div> |
| Built with <a href="http://sphinx-doc.org/">Sphinx</a> using a <a href="https://github.com/rtfd/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>. |
| |
| </footer> |
| |
| </div> |
| </div> |
| |
| </section> |
| |
| </div> |
| |
| |
| |
| <script type="text/javascript"> |
| jQuery(function () { |
| SphinxRtdTheme.Navigation.enable(true); |
| }); |
| </script> |
| |
| |
| |
| |
| |
| |
| </body> |
| </html> |
