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<div class="left-nav__overlay"></div>
<article data-swiftype-index='true'>
<a class='edit-link' href="https://github.com/apache/ignite/tree/IGNITE-7595/docs/_docs/persistence/persistence-tuning.adoc" target="_blank">Edit</a>
<h1>Persistence Tuning</h1>
<div id="preamble">
<div class="sectionbody">
<div class="paragraph">
<p>This article summarizes best practices for Ignite native persistence tuning.
If you are using an external (3rd party) storage for persistence needs, please refer to performance guides from the 3rd party vendor.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="adjusting-page-size">Adjusting Page Size</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The <code>DataStorageConfiguration.pageSize</code> parameter should be no less than the lower of: the page size of your storage media (SSD, Flash, HDD, etc.) and the cache page size of your operating system.
The default value is 4KB.</p>
</div>
<div class="paragraph">
<p>The operating system&#8217;s cache page size can be easily checked using
<a href="https://unix.stackexchange.com/questions/128213/how-is-page-size-determined-in-virtual-address-space" target="_blank" rel="noopener">system tools and parameters</a>.</p>
</div>
<div class="paragraph">
<p>The page size of the storage device such as SSD is usually noted in the device specification. If the manufacturer does not disclose this information, try to run SSD benchmarks to figure out the number.
Many manufacturers have to adapt their drivers for 4 KB random-write workloads because a variety of standard
benchmarks use 4 KB by default.
<a href="https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/ssd-server-storage-applications-paper.pdf" target="_blank" rel="noopener">This white paper</a> from Intel confirms that 4 KB should be enough.</p>
</div>
<div class="paragraph">
<p>Once you pick the most optimal page size, apply it in your cluster configuration:</p>
</div>
<code-tabs><code-tab data-tab='XML'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="xml"><span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.IgniteConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"dataStorageConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.DataStorageConfiguration"</span><span class="nt">&gt;</span>
<span class="c">&lt;!-- Set the page size to 8 KB --&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"pageSize"</span> <span class="na">value=</span><span class="s">"#{8 * 1024}"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/bean&gt;</span>
<span class="nt">&lt;/property&gt;</span>
<span class="nt">&lt;/bean&gt;</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='Java'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="java"><span class="nc">IgniteConfiguration</span> <span class="n">cfg</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">IgniteConfiguration</span><span class="o">();</span>
<span class="c1">// Durable memory configuration.</span>
<span class="nc">DataStorageConfiguration</span> <span class="n">storageCfg</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">DataStorageConfiguration</span><span class="o">();</span>
<span class="c1">// Changing the page size to 8 KB.</span>
<span class="n">storageCfg</span><span class="o">.</span><span class="na">setPageSize</span><span class="o">(</span><span class="mi">8192</span><span class="o">);</span>
<span class="n">cfg</span><span class="o">.</span><span class="na">setDataStorageConfiguration</span><span class="o">(</span><span class="n">storageCfg</span><span class="o">);</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='C#/.NET'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="csharp"><span class="kt">var</span> <span class="n">cfg</span> <span class="p">=</span> <span class="k">new</span> <span class="n">IgniteConfiguration</span>
<span class="p">{</span>
<span class="n">DataStorageConfiguration</span> <span class="p">=</span> <span class="k">new</span> <span class="n">DataStorageConfiguration</span>
<span class="p">{</span>
<span class="c1">// Changing the page size to 4 KB.</span>
<span class="n">PageSize</span> <span class="p">=</span> <span class="m">4096</span>
<span class="p">}</span>
<span class="p">};</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='C++' data-unavailable='true'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code>This API is not presently available for C++. You can use XML configuration.</code></pre>
</div>
</div></code-tab></code-tabs>
</div>
</div>
<div class="sect1">
<h2 id="keep-wals-separately">Keep WALs Separately</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Consider using separate drives for data files and <a href="/docs/2.9.0/persistence/native-persistence#write-ahead-log">Write-Ahead-Logging (WAL)</a>.
Ignite actively writes to both the data and WAL files.</p>
</div>
<div class="paragraph">
<p>The example below shows how to configure separate paths for the data storage, WAL, and WAL archive:</p>
</div>
<code-tabs><code-tab data-tab='XML'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="xml"><span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.IgniteConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"dataStorageConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.DataStorageConfiguration"</span><span class="nt">&gt;</span>
<span class="c">&lt;!--
Sets a path to the root directory where data and indexes are
to be persisted. It's assumed the directory is on a separated SSD.
--&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"storagePath"</span> <span class="na">value=</span><span class="s">"/opt/persistence"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"walPath"</span> <span class="na">value=</span><span class="s">"/opt/wal"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"walArchivePath"</span> <span class="na">value=</span><span class="s">"/opt/wal-archive"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/bean&gt;</span>
<span class="nt">&lt;/property&gt;</span>
<span class="nt">&lt;/bean&gt;</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='Java'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="java"><span class="nc">IgniteConfiguration</span> <span class="n">cfg</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">IgniteConfiguration</span><span class="o">();</span>
<span class="c1">// Configuring Native Persistence.</span>
<span class="nc">DataStorageConfiguration</span> <span class="n">storeCfg</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">DataStorageConfiguration</span><span class="o">();</span>
<span class="c1">// Sets a path to the root directory where data and indexes are to be persisted.</span>
<span class="c1">// It's assumed the directory is on a separated SSD.</span>
<span class="n">storeCfg</span><span class="o">.</span><span class="na">setStoragePath</span><span class="o">(</span><span class="s">"/ssd/storage"</span><span class="o">);</span>
<span class="c1">// Sets a path to the directory where WAL is stored.</span>
<span class="c1">// It's assumed the directory is on a separated HDD.</span>
<span class="n">storeCfg</span><span class="o">.</span><span class="na">setWalPath</span><span class="o">(</span><span class="s">"/wal"</span><span class="o">);</span>
<span class="c1">// Sets a path to the directory where WAL archive is stored.</span>
<span class="c1">// The directory is on the same HDD as the WAL.</span>
<span class="n">storeCfg</span><span class="o">.</span><span class="na">setWalArchivePath</span><span class="o">(</span><span class="s">"/wal/archive"</span><span class="o">);</span>
<span class="n">cfg</span><span class="o">.</span><span class="na">setDataStorageConfiguration</span><span class="o">(</span><span class="n">storeCfg</span><span class="o">);</span>
<span class="c1">// Starting the node.</span>
<span class="nc">Ignite</span> <span class="n">ignite</span> <span class="o">=</span> <span class="nc">Ignition</span><span class="o">.</span><span class="na">start</span><span class="o">(</span><span class="n">cfg</span><span class="o">);</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='C#/.NET'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="csharp"><span class="kt">var</span> <span class="n">cfg</span> <span class="p">=</span> <span class="k">new</span> <span class="n">IgniteConfiguration</span>
<span class="p">{</span>
<span class="n">DataStorageConfiguration</span> <span class="p">=</span> <span class="k">new</span> <span class="n">DataStorageConfiguration</span>
<span class="p">{</span>
<span class="c1">// Sets a path to the root directory where data and indexes are to be persisted.</span>
<span class="c1">// It's assumed the directory is on a separated SSD.</span>
<span class="n">StoragePath</span> <span class="p">=</span> <span class="s">"/ssd/storage"</span><span class="p">,</span>
<span class="c1">// Sets a path to the directory where WAL is stored.</span>
<span class="c1">// It's assumed the directory is on a separated HDD.</span>
<span class="n">WalPath</span> <span class="p">=</span> <span class="s">"/wal"</span><span class="p">,</span>
<span class="c1">// Sets a path to the directory where WAL archive is stored.</span>
<span class="c1">// The directory is on the same HDD as the WAL.</span>
<span class="n">WalArchivePath</span> <span class="p">=</span> <span class="s">"/wal/archive"</span>
<span class="p">}</span>
<span class="p">};</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='C++' data-unavailable='true'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code>This API is not presently available for C++. You can use XML configuration.</code></pre>
</div>
</div></code-tab></code-tabs>
</div>
</div>
<div class="sect1">
<h2 id="increasing-wal-segment-size">Increasing WAL Segment Size</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The default WAL segment size (64 MB) may be inefficient in high load scenarios because it causes WAL to switch between segments too frequently and switching/rotation is a costly operation. Setting the segment size to a higher value (up to 2 GB) may help reduce the number of switching operations. However, the tradeoff is that this will increase the overall volume of the write-ahead log.</p>
</div>
<div class="paragraph">
<p>See <a href="/docs/2.9.0/persistence/native-persistence#changing-wal-segment-size">Changing WAL Segment Size</a> for details.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="changing-wal-mode">Changing WAL Mode</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Consider other WAL modes as alternatives to the default mode. Each mode provides different degrees of reliability in
case of node failure and that degree is inversely proportional to speed, i.e. the more reliable the WAL mode, the
slower it is. Therefore, if your use case does not require high reliability, you can switch to a less reliable mode.</p>
</div>
<div class="paragraph">
<p>See <a href="/docs/2.9.0/persistence/native-persistence#wal-modes">WAL Modes</a> for more details.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="disabling-wal">Disabling WAL</h2>
<div class="sectionbody">
<div class="paragraph">
<p>There are situations where <a href="/docs/2.9.0/persistence/native-persistence#disabling-wal">disabling the WAL</a> can help improve performance.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="pages-writes-throttling">Pages Writes Throttling</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Ignite periodically starts the <a href="/docs/2.9.0/persistence/native-persistence#checkpointing">checkpointing process</a> that syncs dirty pages from memory to disk. A dirty page is a page that was updated in RAM but was not written to a respective partition file (an update was just appended to the WAL). This process happens in the background without affecting the application&#8217;s logic.</p>
</div>
<div class="paragraph">
<p>However, if a dirty page, scheduled for checkpointing, is updated before being written to disk, its previous state is copied to a special region called a checkpointing buffer.
If the buffer gets overflowed, Ignite will stop processing all updates until the checkpointing is over.
As a result, write performance can drop to zero as shown in​ this diagram, until the checkpointing cycle is completed:</p>
</div>
<div class="imageblock">
<div class="content">
<img src="/docs/2.9.0/images/checkpointing-chainsaw.png" alt="Checkpointing Chainsaw">
</div>
</div>
<div class="paragraph">
<p>The same situation occurs if the dirty pages threshold is reached again while the checkpointing is in progress.
This will force Ignite to schedule one more checkpointing execution and to halt all the update operations until the first checkpointing cycle is over.</p>
</div>
<div class="paragraph">
<p>Both situations usually arise when either a disk device is slow or the update rate is too intensive.
To mitigate and prevent these performance drops, consider enabling the pages write throttling algorithm.
The algorithm brings the performance of update operations down to the speed of the disk device whenever the checkpointing buffer fills in too fast or the percentage of dirty pages soar rapidly.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">
<h3 id="pages-write-throttling-in-a-nutshell" class="discrete">Pages Write Throttling in a Nutshell</h3>
<div class="paragraph">
<p>Refer to the <a href="https://cwiki.apache.org/confluence/display/IGNITE/Ignite+Persistent+Store+-+under+the+hood#IgnitePersistentStore-underthehood-PagesWriteThrottling" target="_blank" rel="noopener">Ignite wiki page</a> maintained by Apache Ignite persistence experts to get more details about throttling and its causes.</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>The example below shows how to enable write throttling:</p>
</div>
<code-tabs><code-tab data-tab='XML'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="xml"><span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.IgniteConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"dataStorageConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.DataStorageConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"writeThrottlingEnabled"</span> <span class="na">value=</span><span class="s">"true"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/bean&gt;</span>
<span class="nt">&lt;/property&gt;</span>
<span class="nt">&lt;/bean&gt;</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='Java'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="java"><span class="nc">IgniteConfiguration</span> <span class="n">cfg</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">IgniteConfiguration</span><span class="o">();</span>
<span class="c1">// Configuring Native Persistence.</span>
<span class="nc">DataStorageConfiguration</span> <span class="n">storeCfg</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">DataStorageConfiguration</span><span class="o">();</span>
<span class="c1">// Enabling the writes throttling.</span>
<span class="n">storeCfg</span><span class="o">.</span><span class="na">setWriteThrottlingEnabled</span><span class="o">(</span><span class="kc">true</span><span class="o">);</span>
<span class="n">cfg</span><span class="o">.</span><span class="na">setDataStorageConfiguration</span><span class="o">(</span><span class="n">storeCfg</span><span class="o">);</span>
<span class="c1">// Starting the node.</span>
<span class="nc">Ignite</span> <span class="n">ignite</span> <span class="o">=</span> <span class="nc">Ignition</span><span class="o">.</span><span class="na">start</span><span class="o">(</span><span class="n">cfg</span><span class="o">);</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='C#/.NET'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="csharp"><span class="kt">var</span> <span class="n">cfg</span> <span class="p">=</span> <span class="k">new</span> <span class="n">IgniteConfiguration</span>
<span class="p">{</span>
<span class="n">DataStorageConfiguration</span> <span class="p">=</span> <span class="k">new</span> <span class="n">DataStorageConfiguration</span>
<span class="p">{</span>
<span class="n">WriteThrottlingEnabled</span> <span class="p">=</span> <span class="k">true</span>
<span class="p">}</span>
<span class="p">};</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='C++' data-unavailable='true'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code>This API is not presently available for C++. You can use XML configuration.</code></pre>
</div>
</div></code-tab></code-tabs>
</div>
</div>
<div class="sect1">
<h2 id="adjusting-checkpointing-buffer-size">Adjusting Checkpointing Buffer Size</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The size of the checkpointing buffer, explained in the previous section, is one of the checkpointing process triggers.</p>
</div>
<div class="paragraph">
<p>The default buffer size is calculated as a function of the <a href="/docs/2.9.0/memory-configuration/data-regions">data region</a> size:</p>
</div>
<table class="tableblock frame-all grid-all stripes-even stretch">
<colgroup>
<col style="width: 33.3333%;">
<col style="width: 66.6667%;">
</colgroup>
<thead>
<tr>
<th class="tableblock halign-left valign-top">Data Region Size</th>
<th class="tableblock halign-left valign-top">Default Checkpointing Buffer Size</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">&lt; 1 GB</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">MIN (256 MB, Data_Region_Size)</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">between 1 GB and 8 GB</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">Data_Region_Size / 4</p></td>
</tr>
<tr>
<td class="tableblock halign-left valign-top"><p class="tableblock">&gt; 8 GB</p></td>
<td class="tableblock halign-left valign-top"><p class="tableblock">2 GB</p></td>
</tr>
</tbody>
</table>
<div class="paragraph">
<p>The default buffer size can be suboptimal for write-intensive workloads because the page write throttling algorithm will slow down your writes whenever the size reaches the critical mark.
To keep write performance at the desired pace while the checkpointing is in progress, consider increasing
<code>DataRegionConfiguration.checkpointPageBufferSize</code> and enabling write throttling to prevent performance​ drops:</p>
</div>
<code-tabs><code-tab data-tab='XML'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="xml"><span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.IgniteConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"dataStorageConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.DataStorageConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"writeThrottlingEnabled"</span> <span class="na">value=</span><span class="s">"true"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"defaultDataRegionConfiguration"</span><span class="nt">&gt;</span>
<span class="nt">&lt;bean</span> <span class="na">class=</span><span class="s">"org.apache.ignite.configuration.DataRegionConfiguration"</span><span class="nt">&gt;</span>
<span class="c">&lt;!-- Enabling persistence. --&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"persistenceEnabled"</span> <span class="na">value=</span><span class="s">"true"</span><span class="nt">/&gt;</span>
<span class="c">&lt;!-- Increasing the buffer size to 1 GB. --&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"checkpointPageBufferSize"</span> <span class="na">value=</span><span class="s">"#{1024L * 1024 * 1024}"</span><span class="nt">/&gt;</span>
<span class="nt">&lt;/bean&gt;</span>
<span class="nt">&lt;/property&gt;</span>
<span class="nt">&lt;/bean&gt;</span>
<span class="nt">&lt;/property&gt;</span>
<span class="nt">&lt;/bean&gt;</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='Java'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="java"><span class="nc">IgniteConfiguration</span> <span class="n">cfg</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">IgniteConfiguration</span><span class="o">();</span>
<span class="c1">// Configuring Native Persistence.</span>
<span class="nc">DataStorageConfiguration</span> <span class="n">storeCfg</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">DataStorageConfiguration</span><span class="o">();</span>
<span class="c1">// Enabling the writes throttling.</span>
<span class="n">storeCfg</span><span class="o">.</span><span class="na">setWriteThrottlingEnabled</span><span class="o">(</span><span class="kc">true</span><span class="o">);</span>
<span class="c1">// Increasing the buffer size to 1 GB.</span>
<span class="n">storeCfg</span><span class="o">.</span><span class="na">getDefaultDataRegionConfiguration</span><span class="o">().</span><span class="na">setCheckpointPageBufferSize</span><span class="o">(</span><span class="mi">1024L</span> <span class="o">*</span> <span class="mi">1024</span> <span class="o">*</span> <span class="mi">1024</span><span class="o">);</span>
<span class="n">cfg</span><span class="o">.</span><span class="na">setDataStorageConfiguration</span><span class="o">(</span><span class="n">storeCfg</span><span class="o">);</span>
<span class="c1">// Starting the node.</span>
<span class="nc">Ignite</span> <span class="n">ignite</span> <span class="o">=</span> <span class="nc">Ignition</span><span class="o">.</span><span class="na">start</span><span class="o">(</span><span class="n">cfg</span><span class="o">);</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='C#/.NET'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="csharp"><span class="kt">var</span> <span class="n">cfg</span> <span class="p">=</span> <span class="k">new</span> <span class="n">IgniteConfiguration</span>
<span class="p">{</span>
<span class="n">DataStorageConfiguration</span> <span class="p">=</span> <span class="k">new</span> <span class="n">DataStorageConfiguration</span>
<span class="p">{</span>
<span class="n">WriteThrottlingEnabled</span> <span class="p">=</span> <span class="k">true</span><span class="p">,</span>
<span class="n">DefaultDataRegionConfiguration</span> <span class="p">=</span> <span class="k">new</span> <span class="n">DataRegionConfiguration</span>
<span class="p">{</span>
<span class="n">Name</span> <span class="p">=</span> <span class="n">DataStorageConfiguration</span><span class="p">.</span><span class="n">DefaultDataRegionName</span><span class="p">,</span>
<span class="n">PersistenceEnabled</span> <span class="p">=</span> <span class="k">true</span><span class="p">,</span>
<span class="c1">// Increasing the buffer size to 1 GB.</span>
<span class="n">CheckpointPageBufferSize</span> <span class="p">=</span> <span class="m">1024L</span> <span class="p">*</span> <span class="m">1024</span> <span class="p">*</span> <span class="m">1024</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="p">};</span></code></pre>
</div>
</div></code-tab><code-tab data-tab='C++' data-unavailable='true'><div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code>This API is not presently available for C++. You can use XML configuration.</code></pre>
</div>
</div></code-tab></code-tabs>
<div class="paragraph">
<p>In the example above, the checkpointing buffer size of the default region is set to 1 GB.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="enabling-direct-io">Enabling Direct I/O</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Usually, whenever an application reads data from disk, the OS gets the data and puts it in a file buffer cache first.
Similarly, for every write operation, the OS first writes the data in the cache and transfers it to disk later. To
eliminate this process, you can enable Direct I/O in which case the data is read and written directly from/to the
disk, bypassing the file buffer cache.</p>
</div>
<div class="paragraph">
<p>The Direct I/O module in Ignite is used to speed up the checkpointing process, which writes dirty pages from RAM to disk. Consider using the Direct I/O plugin for write-intensive workloads.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">
<h3 id="direct-io-and-wals" class="discrete">Direct I/O and WALs</h3>
<div class="paragraph">
<p>Note that Direct I/O cannot be enabled specifically for WAL files. However, enabling the Direct I/O module provides
a slight benefit regarding the WAL files as well: the WAL data will not be stored in the OS buffer cache for too long;
it will be flushed (depending on the WAL mode) at the next page cache scan and removed from the page cache.</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>You can enable Direct I/O, move the <code>{IGNITE_HOME}/libs/optional/ignite-direct-io</code> folder to the upper level <code>libs/optional/ignite-direct-io</code> folder in your Ignite distribution or as a Maven dependency as described <a href="/docs/2.9.0/setup#enabling-modules">here</a>.</p>
</div>
<div class="paragraph">
<p>You can use the <code>IGNITE_DIRECT_IO_ENABLED</code> system property to enable or disable the plugin at runtime.</p>
</div>
<div class="paragraph">
<p>Get more details from the <a href="https://cwiki.apache.org/confluence/display/IGNITE/Ignite+Persistent+Store+-+under+the+hood#IgnitePersistentStore-underthehood-DirectI/O" target="_blank" rel="noopener">Ignite Direct I/O Wiki section</a>.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="purchase-production-level-ssds">Purchase Production-Level SSDs</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Note that the performance of Ignite Native Persistence may drop after several hours of intensive write load due to
the nature of how <a href="http://codecapsule.com/2014/02/12/coding-for-ssds-part-2-architecture-of-an-ssd-and-benchmarking" target="_blank" rel="noopener">SSDs are designed and operate</a>.
Consider buying fast production-level SSDs to keep the performance high or switch to non-volatile memory devices like
Intel Optane Persistent Memory.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="ssd-over-provisioning">SSD Over-provisioning</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Performance of random writes on a 50% filled disk is much better than on a 90% filled disk because of the SSDs over-provisioning (see <a href="https://www.seagate.com/tech-insights/ssd-over-provisioning-benefits-master-ti" target="_blank" rel="noopener"><a href="https://www.seagate.com/tech-insights/ssd-over-provisioning-benefits-master-ti" class="bare">https://www.seagate.com/tech-insights/ssd-over-provisioning-benefits-master-ti</a></a>).</p>
</div>
<div class="paragraph">
<p>Consider buying SSDs with higher over-provisioning rates and make sure the manufacturer provides the tools to adjust it.</p>
</div>
<div class="admonitionblock note">
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<div class="title">Note</div>
</td>
<td class="content">
<h3 id="intel-3d-xpoint" class="discrete">Intel 3D XPoint</h3>
<div class="paragraph">
<p>Consider using 3D XPoint drives instead of regular SSDs to avoid the bottlenecks caused by a low over-provisioning
setting and constant garbage collection at the SSD level.
Read more <a href="http://dmagda.blogspot.com/2017/10/3d-xpoint-outperforms-ssds-verified-on.html" target="_blank" rel="noopener">here</a>.</p>
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