In computing, specifically in Unix and Unix-like operating systems, a raw device is a special kind of logical device associated with a character device file that allows a storage device such as a hard disk drive to be accessed directly, bypassing the operating system's caches and buffers (although the hardware caches might still be used).
Applications like a database management system can use raw devices directly, enabling them to manage how data is cached, rather than deferring this task to the operating system.
Support for non-raw devices was removed in FreeBSD 4.0 in order to simplify buffer management and increase scalability and performance.
[1] In Linux, opening a block device with the O_DIRECT flag replaces raw device usage.
Raw devices were removed entirely from the Linux kernel in the 5.14 release.