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| <section id="durable-memory" class="page-section"> |
| <h1 class="first">Durable Memory</h1> |
| <div class="col-sm-12 col-md-12 col-xs-12" style="padding-left:0; padding-right:0;"> |
| <div class="col-sm-6 col-md-7 col-xs-12" style="padding-left:0; padding-right:0;"> |
| <p> |
| Apache Ignite is based on the <nobr>Durable Memory</nobr> |
| architecture that allows storing and processing data and indexes both in memory and on disk |
| when the <a href="/arch/persistence.html">Ignite Native Persistence</a> feature is enabled. |
| </p> |
| <p> |
| The durable memory architecture helps achieve the performance and scale of in-memory computing |
| together with the disk durability and strong consistency in one system. |
| </p> |
| </div> |
| |
| <div class="col-sm-6 col-md-5 col-xs-12" style="padding-right:0; top: -10px;"> |
| <img class="img-responsive" src="/images/durable_memory.png" width="440px" style="float:right;"/> |
| </div> |
| </div> |
| <p> |
| Ignite's Durable Memory operates in a way similar to the Virtual Memory of operating systems |
| such as Linux. However, one significant difference between these two is that the Durable Memory, |
| in addition to keeping the whole or partial data set in memory, always keeps the whole data set with |
| indexes on disk (assuming that Ignite Native Persistence is enabled), while Virtual Memory uses the |
| disk when it runs out of RAM, for swapping purposes only. |
| </p> |
| |
| <div class="page-heading" id="durable-memory-modes"> |
| Durable Memory Modes |
| <a href="/arch/durablememory.html#durable-memory-modes"><i class="fa fa-anchor"></i></a> |
| </div> |
| <table class="formatted" name="Deployment Options Features"> |
| <thead> |
| <tr> |
| <th width="35%" class="left">Mode</th> |
| <th>Description</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td class="left">In-Memory</td> |
| <td> |
| <p> |
| The whole data set is stored in memory. In this scenario, you can achieve the maximum |
| performance possible because the data is never written to disk. To prevent possible data |
| loss when a single cluster node fails, it is recommended to configure a number of backup |
| copies (aka. replication factor) appropriately. |
| <a href="/arch/durablememory.html#swap-space">Swap space</a> can be used to prevent memory |
| overflow. |
| </p> |
| |
| <p> |
| <strong>Use cases</strong>: in-memory caches, in-memory data grids, in-memory computations, |
| web-session caching, real-time processing of continuous data streams. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td class="left">In-Memory + 3rd party database</td> |
| <td> |
| <p> |
| Ignite can be used as a caching layer (aka. data grid) above an existing 3rd party |
| database - RDBMS, NoSQL, or HDFS. This mode is used to accelerate the underlying database. |
| Automatic integration is provided with most of the known databases, like Oracle, MySQL, |
| PostgreSQL, Apache Cassandra, etc. |
| </p> |
| |
| <p> |
| <strong>Use cases</strong>: Ignite as <a href="/features/datagrid.html">In-Memory Data Grid</a> |
| - adds acceleration and scale to existing database deployments (RDBMS, NoSQL, etc). |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td class="left">In-Memory + Full Copy on Disk</td> |
| <td> |
| <p> |
| The whole data set is stored in memory and on disk. The disk is used for data recovery |
| purposes in case of full cluster crashes and restarts. |
| <a href="/arch/durablememory.html#native-persistence">Ignite native persistence</a> is used to |
| store the data on disk. |
| </p> |
| |
| <p> |
| <strong>Use cases</strong>: Ignite as an |
| <a href="/use-cases/database/in-memory-database.html"><nobr>In-Memory Database</nobr></a> - |
| provides SQL, key-value and collocated processing APIs to in-memory data. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td class="left">100% on Disk + In-Memory Cache</td> |
| <td> |
| <p> |
| 100% of data is stored in <a href="/arch/durablememory.html#native-persistence">Ignite native |
| persistence</a> and smaller subset of data is cached in memory. The more data is cached in |
| memory, the faster is the performance. The disk serves as the primary storage that survives |
| any type of cluster failures and restarts. |
| </p> |
| |
| <p> |
| <strong>Use cases</strong>: Ignite as a |
| <a href="/use-cases/database/distributed-database.html">Memory-Centric Distributed Database</a> |
| - provides cloud-native distributed database with SQL, key-value and collocated processing APIs. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| |
| <h2 style="padding-top: 10px;" id="native-persistence"> |
| Ignite Native Persistence |
| <a href="/arch/durablememory.html#native-persistence"><i class="fa fa-anchor"></i></a> |
| </h2> |
| <p> |
| Ignite Persistence is the most flexible, scalable, and convenient way of persisting data in Ignite. |
| It is widely used in scenarios where applications need a distributed memory-centric database |
| </p> |
| <p> |
| Ignite native persistence is a distributed, ACID, and <nobr>SQL-compliant</nobr> disk store |
| that transparently integrates with Ignite's durable memory. Ignite persistence is optional |
| and can be turned on and off. When turned off Ignite becomes a pure in-memory store. |
| </p> |
| <p> |
| Following are the advantages and characteristics of Apache Ignite as a platform when Durable Memory |
| and Ignite Native Persistence are used together: |
| </p> |
| <div class="col-sm-6 col-md-6 col-xs-12" style="padding-left:0; padding-right:0;"> |
| <div class="page-heading">In-Memory</div> |
| <ul class="page-list"> |
| <li>Off-Heap memory</li> |
| <li>Removes noticeable GC pauses</li> |
| <li>Automatic Defragmentation</li> |
| <li>Predictable memory consumption</li> |
| <li>Boosts SQL performance</li> |
| </ul> |
| </div> |
| <div class="col-sm-6 col-md-6 col-xs-12" style="padding-left:0; padding-right:0;"> |
| <div class="page-heading">On Disk</div> |
| <ul class="page-list"> |
| <li>Optional Persistence</li> |
| <li>Support of flash, SSD, Intel 3D Xpoint</li> |
| <li>Stores superset of data</li> |
| <li>Fully Transactional</li> |
| <ul> |
| <li>Write-Ahead-Log (WAL)</li> |
| </ul> |
| <li>Instantaneous Cluster Restarts</li> |
| </ul> |
| </div> |
| |
| <h2 style="padding-top: 10px;" id="3rd-party-persistence"> |
| 3rd Party Persistence |
| <a href="/arch/durablememory.html#3rd-party-persistence"><i class="fa fa-anchor"></i></a> |
| </h2> |
| <p> |
| Ignite can be used as a caching layer (aka. data grid) above an existing 3rd party |
| database - RDBMS, NoSQL, or HDFS. This mode is used to accelerate the underlying database that persists |
| the data. Ignite stores data in memory, distributed across multiple nodes providing fast data access. |
| It reduces the network overhead caused due to frequent data movement between an application and the database. |
| However, there are some limitations in comparison to the native persistence. For instance, SQL queries |
| will be executed only on the data that is in RAM, thus, requiring to preload all the data set from disk |
| to memory beforehand. |
| </p> |
| |
| <h2 style="padding-top: 10px;" id="swap-space"> |
| Swap Space |
| <a href="/arch/durablememory.html#swap-space"><i class="fa fa-anchor"></i></a> |
| </h2> |
| <p> |
| If you do not want to use Ignite native persistence or 3rd party persistence, you can enable swapping, |
| in which case, Ignite in-memory data will be moved to the swap space located on disk if you run out of RAM. |
| When swap space is enabled, Ignites stores data in memory mapped files (MMF) whose content will be |
| swapped to disk by the OS depending on the current RAM consumption. The swap space is mostly used to |
| avoid out of memory errors (OOME) that might happen if RAM consumption goes beyond its capacity and |
| you need more time to scale the cluster out to redistribute the data sets evenly. |
| </p> |
| |
| <div class="page-heading">More Information</div> |
| <p><a href="https://apacheignite.readme.io/docs/durable-memory" target="_blank" rel="noopener">Durable Memory</a></p> |
| <p><a href="https://apacheignite.readme.io/docs/distributed-persistent-store" target="_blank" rel="noopener">Native Persistence</a></p> |
| <p><a href="https://apacheignite.readme.io/docs/3rd-party-store" target="_blank" rel="noopener">3rd Party Persistence</a></p> |
| <p><a href="https://apacheignite.readme.io/docs/swap-space" target="_blank" rel="noopener">Swap Space</a></p> |
| </section> |
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