Raw drive is the basic form of the computer hard drive or any storage device. It has no file system and thus is an uninitialized drive, which is not an ideal one to store data. No regulation or no file system, your files will be not be in an organized way. With Raw drives, files are accessed directly on the byte-stream of your drive without any restrictions imposed by the OS.
In general, operating system of the computer will read the disk with the help of the file system and then tracks the location of each file. However, a raw drive doesn’t have any file system; hence it reads the data in the binary level i.e. one bit at a time, which bypasses the file system.
Raw drives acts as the last chance for all I / O requests to be processed that requires file system support. When the I / O manager requests all the active file systems to mount a Volume, Raw is called last since, it can support all disk and tape media and can operate and fetch data without the aid of any file systems like FAT, NTFS etc. A Raw disk offers elementary file handling capabilities, it means whenever a read / write request is received on the physical disk, it just allows the user to access the logical blocks of data on the physical disk without imposing any on-disk or metadata restrictions for accessing the information. It treats entire disk as a single file and offers physical-disk-level access to the drive.
If a device is being driven in raw mode, it will not possess any function driver and upper or lower-level filter drives. However, it uses the bus-driver and the optional-filter drivers instead.
Uses of Raw disks:
A raw disk format is often useful in cases data loss situations like deletion, file system or creating the disk image of the drive having bad sectors etc. in order to recover data.
Trying to edit the raw disks is very risk as work with the byte-values in these raw drives. Hence, even if a single byte goes missing, it results in operating system reinstalling thus causing huge loss of data. In case you end up in such a situation, refer this page as this will help you in raw partition recovery.