December 5, 2001

New Linux-based benchmark sheds light on main memory vs. RAM-disk databases

Author: JT Smith

Ted Kenney writes, "It stands to reason that accessing data from memory will be faster than from physical media. Developers of embedded systems on Linux are encountering a new type of DBMS, the main memory database (MMDB), which claims breakthrough performance and availability via memory-only processing.

But doesn't database caching achieve the same result? And if complete elimination of disk access is the goal, why not deploy a traditional database on a RAM-disk, which creates a file system in memory?

McObject's new white paper, "Main Memory vs. RAM-Disk Databases: A Linux-based Comparison" addresses performance and availability implications of different approaches to database management in embedded systems running on Linux. The paper is available at

McObject's benchmark tests the company's MMDB against a widely used embedded database, db.linux, which is used in both traditional (disk-based) and RAM-disk modes. Deployment on RAM-disk boosts the traditional database?s performance by as much as 74 percent, but still lags the memory-only database in this test, performed on Red Hat Linux version 6.2.

Fundamental architectural differences explain the disparity. Performance overhead in disk-based databases includes data transfer and duplication, unneeded recovery logic and, ironically, caching functions intended to avoid disk access. None of these can be "turned off" when the database is deployed in memory. In contrast, the MMDB is streamlined to provide only the functions required for memory-based data management in real-time embedded systems.

More information about McObject is available at

Click Here!