Difference between Raw Device and Block Device
A RAW Device read/write 0 or more bytes, in a stream and can be opened using Direct I/O. RAW devices can be faster for certain applications like databases because they does not contain a file system, and they don’t use cache for the same reason. You don’t mount a RAW device.
A BLOCK device would read/write bytes in fixed size blocks, as in disk sectors. The block device is cached. I/O to the device is read into memory, referred to as buffer cache, in large blocks.The block devices are used to mount filesystems. Each disk has a block device interface where the system makes the device byte addressable and you can write a single byte in the middle of the disk.