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What is the Difference between a SATA and RAID Controller?

written by: M.S. Smith•edited by: Simon Hill•updated: 4/25/2010

Controllers are an important, but often forgotten, part of computer storage. They are responsible for making access to long term computer memory fast and seamless. This article explains the difference between two storage related controllers known as SATA and RAID controllers.

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    Explaining SATA and RAID Controllers

    SATA. RAID. These are acronyms with specific definitions, but to those who are learning about computer storage technology they look like nothing more than a bunch of gibberish. Worse, understanding what SATA and RAID, and what the controllers for each do, is further confused by how closely related the two terms are. In fact, many stores will lump SATA and RAID controllers in the same simple heading of "controller" making it difficult to understand where the purpose of one begins and another ends.

    This guide will provide a quick over-view of how SATA and RAID controllers differ. But first, let's take a look at what, exactly, a controller is.

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    What is a Controller?

    Difference between SATA and RAID Controller A controller is a piece of hardware or software which controls how storage devices connected to a system work. The process of moving data smoothly is very complex and requires careful calculations about the order in which data should be accessed, what data should be sent where, and what data should be kept in the cache in order to provide more rapid overall access to data.

    Controllers can be either hardware or software solutions. Hardware controllers are physical processors. Hardware controllers are very common and can be found on all hard drives and motherboards. Software controllers are software which mimic a hardware controller by tapping into the power of the computer's CPU. Software controllers are most often RAID controllers, but there are also many hardware RAID controllers.

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    So, What's the Difference?

    SATA stands for Serial ATA and refers to a method of connecting hard drives to a computer. It is the responsibility of the SATA controller to handle how the hard drives connect to a computer's motherboard. Let's say, for example, that you have three SATA hard drives connected to your motherboard. It is up to the SATA controller to decide on the fastest method of relaying data to and from those hard drives and to make sure that the computer does not become confused when information is coming and going from multiple hard drives at the same time.

    RAID stands for Redundent Array of Independent Disks. It is a method through which multiple hard drives are combined in order to create a single usable drive. This gives advantages in performance, redundancy, or both. RAID 1, for example, essentially turns two drives into mirrors of each other so that if one drive fails, data will still be safe on the second. It is the responsibility of the RAID controller to decide how information is read from and written to the two drives and it is also responsible for making the drives work together as if they were a single drive.

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    Are SATA Controllers RAID Controllers, and Vice-Versa?

    No, they're not. SATA and RAID controllers are different things. However, many motherboards and SATA controller cards provide software RAID support which means that RAID configurations can be used without a hardware RAID controller. This can cause confusion and can lead users into believing they have a physical RAID controller when in fact they only have a software RAID controller.

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    A Note on SATA and RAID Cards

    Don't confuse the word card with controller. Many SATA and RAID cards are sold, but they're not necessarily cards which have a dedicated controller. Be sure to read the specifications of what you are buying very closely to ensure that the product you are purchasing is capable of the tasks you require.