RDSK vs DSK
RDSK and DSK are two device paths in Unix like environments where you will find your hard drives. For most people, it seems to be redundant as it looks like they have the same content; but they don’t. DSK is a block device path where you will find all your formatted drives that are ready to be used. In comparison, RDSK is a raw device path and it contains all drives that have not yet been formatted and are thus referred to as RAW.
Formatting a drive is not specific to drive itself but to the operating system. It dictates where and how the bits of data are located so that the OS can find it when it needs to. If the operating system does not know the file system used on the drive, it will be unable to retrieve any files or write new ones; although, it can still write on the drive as if it is RAW and place another file system on it. This is commonly known as reformatting. But nowadays, most modern operating systems like Linux use a set of commonly known file systems that other operating systems are also able to recognize.
As the drive does not have any knowledge about the file system, it is the operating system that intercepts and services the requests to drives listed in DSK. Obviously, there are some performance losses since the OS would need to process the request and find the appropriate space on the disk. But on the positive side, it isn’t really too complex to write anything to the disk as the OS handles all of that. On the other hand, requests to drives in the RDSK don’t get processed by the OS and goes directly to the drive. It doesn’t benefit from things like buffering and optimization. You should also have a good grasp of what you are doing as you need to be sure of where you are reading or writing and how large or small that part should be. Getting something wrong would certainly mean getting incorrect information. Or worse, you could corrupt files or the entire file system.
Summary:
1.DSK is a block device path while RDSK is a raw device path
2.DSK contains formatted drives while RDSK contains unformatted drives
3.DSK requests are processed by the OS while RDSK requests are processed by the drive directly
4.Communicating via RDSK is a more complicated matter than via DSK