Hybrids Database Architecture with In-memory & Disk

When storing data in main memory, gives performance benefits but it is an expensive method of data storage. An approach to realizing the benefits of in-memory storage while limiting its costs is to store the most frequently accessed data in-memory and the rest on disk. This approach is called hybrid architecture of in-memory with Disk. There are some benefits of using hybrid architecture listed below:

• Performance (which is enhanced by sorting, storing and retrieving specified data entirely in memory, rather than going to disk).
• Lower TCO from reduction in hardware investment Cost, because a less costly hard disk can be substituted for more memory.
• Reduced point of failure using Persistence - All data is stored and managed exclusively in RAM is at risk of being lost upon a process or server failure. So every In-memory database 
• provide solution as a persistence to disk. This is usually act like hardening transaction log from memory to disk. Different vendor have different mechanism for persistency. Continuous writing to disk or snapshot on some intervals. 
• Reduced operational costs and human resources.