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RAID Explained in Simple Terms

I find that “RAID” is such a scary term to a lot of my end users or business clients who are not Network Admin’s. A RAID is in it’s simplest form more then one “physical” (physical means the actual device you would hold in you hand) hard drive put together to make one physical array. In most computers if we have 2 hard drives in it then when we go into the disk management utility that is what we will see. We may have multiple logical drives (this means one physical drive split up in to smaller portions) but the machine still knows that physically those drives are separate entities.

In a raid situation the operating system will see multiple drives and one physical device. This is thanks to RAID controllers. A Raid controller is a device that you plug multiple hard drives into and it handles telling the operating system how to deal with the drives as a single array (and array is multiple drives set up to make a single device). The reason it is important now a  days for even the most green of users to understand how this technology works is that a large majority of machines are coming with a RAID 0 configuration. The reason is that mother board manufacturers are including this as just part of their mother board now and the second reason is that you will get better performance from a raid 0 especially if you are a gamer, or running Database applications on a server. People who buy these machines should understand that even though you have a “RAID” it is not a fault tolerant array type, your data is not any safer then it would be on a single drive and actually with the idea that now you’re hoping 2 drives function perfectly you are actually in a more data risky situation. I run a RAID 0 for my BOOT/PROGRAM drive because I do game and I want the boost in access time. I would not recommend running you DATA from these drives.

There are 3 RAID types that are most popular

RAID 0 with is 2 PHYSICAL hard drives put together to make one big drive. Their upside is super fast read write time, the down side would be no fault tolerance so when you lose a  drive it can be an expensive proposition getting your data back.

RAID 1 This is the Mirrored Set we all hear about. it is 2 PHYSICAL drive put together so that you have an exact duplicate of the main drive. The upside is that face that you always have  a backup, downside would be that it is slow for reading and writing because it has to propagate the data on both drive.

RAID 5 This is the ARRAY everyone think about when you say you have a RAID. This is multiple disks (3 or more) put together to make a fault tolerant drive. The idea being that it will write data across all drives duplicating the data in small pieces as it goes. So in theory you can lose a drive and still be running. This kind of array is faster then RAID 1 but extremely temperamental. It requires a technician with some expertise to monitor and maintain because drives can fall out of the array all of the time. (ON A SIDE NOTE: It is always good to install the Raid Controller monitoring software on your machine, it can give vital information as well as email you when the array is have problems and may be able to save you money by keeping you informed so that you will not have to have a RAID recovery done.)

If you have any questions about your RAID please feel free to ask here and I will try and help the best I can. Again I am no RAID expert and this is just how I like to think of all of them in a simple way. Visit our RAID Data Recovery page if you are having problems with your RAID.


6 Responses to “RAID Explained in Simple Terms”

  1. krishnarao August 5, 2009 10:58 pm #

    I have a 500 GB seagate ST 3500630AS HDD(no partitaons). It is working few months
    one day with power failure improper shutdown
    Restart system wondows chekdisk showes currupt MFT chekdisk is abourt.
    After booting system the drive appear but not open and no disply drive size.
    plese help me.
    How can i repair my HDD without data loss in the same drive?

  2. bill October 10, 2009 11:56 am #

    Does Raid-1, using software only, like win NT server, or W2K server, write the MBR on both drives in the array? i.e., can i then split the array, and move either drive to the active position, and expect the pc to boot up properly.

  3. tim October 18, 2009 4:11 am #

    I was wondering what are some of the best books to start learning about computers so I can get a job. I have a good knowledge of computers. but I would like to be wise in microsoft operating systems since that is a the largestmarket and also hardware and widely used software please help thanks

  4. bob February 7, 2013 2:42 pm #

    i have raid 0 set up

    1.. both drives are 250gb, only shows c drive as 250 not 500 on my computer properties ?
    2. can i physically remove one drive and then any bios set up actions required ?

    • David Mohyla February 7, 2013 3:10 pm #

      No. is my initial answer. If you can clone the drive that is not showing up to another drive (preferably the same make and model) and replace it with the cloned new drive. If the drive is not functioning then you have a problem if you need your data. As you know a RAID 0 is a striped set. The stripe is like a zipper moving across the two drives with data split and stored in the size of the stripe.

  5. Sreejith Babu March 10, 2014 11:35 pm #

    Thank you sir for the useful information. You have explained it in very simple words.

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