Apache Ignite Quick Start Guide

IMDB versus IMDG

In-memory databases are fully functional good old RDBMS that store data in memory (RAM). When you make a database query to fetch records or you update a row, you access the RAM instead of the filesystem. RDBMS accesses the disk to seek data and that's why IMDBs are faster than the RDBMS.

Although IMDBs store data in RAM, your data will not be lost when the machine reboots. You can configure an IMDB to recover from machine restarts/crashes. Typically stores data in memory but keeps a transaction log for each operation. The log appends transaction details at the end of the file. When the machine restarts, it reloads data from the transaction log and creates a snapshot, that's it!

So, for each update or insert operation, it ...