Definitions for "Direct I/O"
An I/O scheme that synchronously reads and writes data from a file without copying it to a cache.
Direct I/O differs from normal disk read/writes in that it by-passes the file system's buffer cache. This is achieved by skipping the (normally done) copy that goes from the application memory space to the kernel buffer's memory space. Direct I/O is an SGI/Linux extension. Compare to memory-mapped I/O and POSIX I/O.
An unbuffered form of I/O that bypasses the kernel's buffering of data. With direct I/O, the file system transfers data directly between the disk and the user-supplied buffer. See buffered I/O and unbuffered I/O.