[philsnow]

> If you clearly understand your access patterns and memory requirements, you can often outperform the default OS page cache.

I believe various RDBMSs bypass the page cache and use their own strategies for managing caching if you give them access to raw block devices, right?

[inkyoto]

That is true and correct, except that Linux does not have raw devices, and O_DIRECT on a file is not a complete replacement for the raw devices (the buffer cache still gets involved as well as the file system).