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| <h5 class="page-header text-uppercase">Documentation |
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| <h1 id="snapshot-performance">Snapshot Performance</h1> |
| |
| <p>Periodically the scheduler writes a full snapshot of its state to the replicated log. To do this |
| it needs to hold a global storage write lock while it writes out this data. In large clusters |
| this has been observed to take up to 40 seconds. Long pauses can cause issues in the system, |
| including delays in scheduling new tasks.</p> |
| |
| <p>The scheduler has two optimizations to reduce the size of snapshots and thus improve snapshot |
| performance: compression and deduplication. Most users will want to enable both compression |
| and deduplication.</p> |
| |
| <h2 id="compression">Compression</h2> |
| |
| <p>To reduce the size of the snapshot the DEFLATE algorithm can be applied to the serialized bytes |
| of the snapshot as they are written to the stream. This reduces the total number of bytes that |
| need to be written to the replicated log at the cost of CPU and generally reduces the amount |
| of time a snapshot takes. Most users will want to enable both compression and deduplication.</p> |
| |
| <h3 id="enabling-compression">Enabling Compression</h3> |
| |
| <p>Snapshot compression is enabled via the <code>-deflate_snapshots</code> flag. This is the default since |
| Aurora 0.5.0. All released versions of Aurora can read both compressed and uncompressed snapshots, |
| so there are no backwards compatibility concerns associated with changing this flag.</p> |
| |
| <h3 id="disabling-compression">Disabling compression</h3> |
| |
| <p>Disable compression by passing <code>-deflate_snapshots=false</code>.</p> |
| |
| <h2 id="deduplication">Deduplication</h2> |
| |
| <p>In Aurora 0.6.0 a new snapshot format was introduced. Rather than write one configuration blob |
| per Mesos task this format stores each configuration blob once, and each Mesos task with a |
| pointer to its blob. This format is not backwards compatible with earlier versions of Aurora.</p> |
| |
| <h3 id="enabling-deduplication">Enabling Deduplication</h3> |
| |
| <p>After upgrading Aurora to 0.6.0, enable deduplication with the <code>-deduplicate_snapshots</code> flag. |
| After the first snapshot the cluster will be using the deduplicated format to write to the |
| replicated log. Snapshots are created periodically by the scheduler (according to |
| the <code>-dlog_snapshot_interval</code> flag). An administrator can also force a snapshot operation with |
| <code>aurora_admin snapshot</code>.</p> |
| |
| <h3 id="disabling-deduplication">Disabling Deduplication</h3> |
| |
| <p>To disable deduplication, for example to rollback to Aurora, restart all of the cluster’s |
| schedulers with <code>-deduplicate_snapshots=false</code> and either wait for a snapshot or force one |
| using <code>aurora_admin snapshot</code>.</p> |
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| <p class="disclaimer">© 2014-2017 <a href="http://www.apache.org/">Apache Software Foundation</a>. Licensed under the <a href="http://www.apache.org/licenses/">Apache License v2.0</a>. The <a href="https://www.flickr.com/photos/trondk/12706051375/">Aurora Borealis IX photo</a> displayed on the homepage is available under a <a href="https://creativecommons.org/licenses/by-nc-nd/2.0/">Creative Commons BY-NC-ND 2.0 license</a>. Apache, Apache Aurora, and the Apache feather logo are trademarks of The Apache Software Foundation.</p> |
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