mirror of
https://github.com/scylladb/scylladb.git
synced 2026-05-01 13:45:53 +00:00
35 lines
2.1 KiB
ReStructuredText
35 lines
2.1 KiB
ReStructuredText
Scylla Anti-Entropy
|
||
===================
|
||
|
||
.. toctree::
|
||
:hidden:
|
||
:glob:
|
||
|
||
Scylla Hinted Handoff <hinted-handoff/>
|
||
Scylla Read Repair <read-repair/>
|
||
Scylla Repair </operating-scylla/procedures/maintenance/repair/>
|
||
|
||
|
||
Scylla replicates data according to :term:`eventual consistency<Eventual Consistency>`. This means that, in Scylla, when considering the :term:`CAP Theorem<CAP Theorem>`, availability and partition tolerance are considered a higher priority over consistency. Although Scylla’s tunable consistency allows users to make a tradeoff between availability and consistency, Scylla’s :term:`consistency level<Consistency Level (CL)>` is tunable per query.
|
||
|
||
However, over time, there can be a number of reasons for data inconsistencies, including:
|
||
|
||
1. a down node;
|
||
2. a network partition;
|
||
3. dropped mutations;
|
||
4. process crashes (before a flush);
|
||
5. a replica that cannot write due to being out of resources;
|
||
6. file corruption.
|
||
|
||
To mitigate :term:`entropy<Entropy>`, or data inconsistency, Scylla uses a few different processes. The goal of Scylla :term:`anti-entropy<Anti-Entropy>` - based on that of Apache Cassandra - is to compare data on all replicas, synchronize data between all replicas, and, finally, ensure each replica has the most recent data.
|
||
|
||
Anti-entropy measures include *write-time* changes such as :term:`hinted handoff<Hinted Handoff>`, *read-time* changes such as :term:`read repair<Read Repair>`, and finally, periodic maintenance via :term:`repair<Repair>`.
|
||
|
||
* :doc:`Scylla Hinted Handoff <hinted-handoff/>` - High-Level view of Scylla Hinted Handoff
|
||
* :doc:`Scylla Read Repair <read-repair/>` - High-Level view of Scylla Read Repair
|
||
* :doc:`Scylla Repair </operating-scylla/procedures/maintenance/repair/>` - Description of Scylla Repair
|
||
|
||
Also learn more in the `Cluster Management, Repair and Scylla Manager lesson <https://university.scylladb.com/courses/scylla-operations/lessons/cluster-management-repair-and-scylla-manager/topic/cluster-management-repair-and-scylla-manager/>`_ on Scylla University.
|
||
|
||
.. include:: /rst_include/apache-copyrights.rst
|