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1. Need to be able to use SQL indexes from disk and from memory
2. Need to store both, primary and backups, on disk
3. Persistent Store format should be separated into file-per-partition for easier migration of data
4. Persistent Store needs to be globally transactional and handle scenarios when some nodes committed successfully and others did not
    

4. Webinar: Persistent Store Overview

Watch the recording of the Apache Ignite Community meetup to quickly grasp the benefits, specificities, architecture and implementation details of the store. 

• Recording: Ignite Persistent Store Recording
• Slides: Ignite Persistent Store Slides
• Code base: refer to Ignite Persistent Store clearance form to find the latest branch where the donation is located and get more details.
  
  

5. Design

4.1 Persistent Store

The main purpose of the Persistent Store is to provide data persistence and fault-tolerance, i.e. no data should ever be lost regardless of any type of failures. 

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Apache Ignite will maintain a separate a WAL file for every cacheall caches.  The The purpose of a the WAL file is to provide a fast and efficient mechanism to store the latest recovery mechanism for the transactional data stored on disk. 

WAL update details:

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