Incomputing, specifically inUnix andUnix-like operating systems, araw device is a special kind of logical device associated with a characterdevice file that allows a storage device such as ahard disk drive to be accessed directly, bypassing the operating system'scaches and buffers (although the hardware caches might still be used). Applications like adatabase management system can use raw devices directly, enabling them to manage how data is cached, rather than deferring this task to the operating system.
InFreeBSD, all device files are in fact raw devices. Support for non-raw devices was removed in FreeBSD 4.0 in order to simplify buffer management and increase scalability and performance.[1]
InLinux, opening a block device with theO_DIRECT flag replaces raw device usage. Raw devices were removed entirely from theLinux kernel in the 5.14 release.[2]
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