How can I combine multiple hard drives in an operating system?

Marc December 13, 2011

How do I setup a computer I am building that will use two 40GB hard drives as if the two drives were one 80GB drive? Does the system ask which drive I wish to use for both the OS and susequent downloads? Every time? Can I make a choice so that drive “C” is primary and drive “X” is the secondary?

  1. Anonymous
    December 14, 2011 at 1:52 pm

    RAID 1 is usually implemented as mirroring; a drive has its data duplicated on
    two different drives using either a hardware RAID controller or software
    (generally via the operating system). If either drive fails, the other continues
    to function as a single drive until the failed drive is replaced.
    Supported by all hardware controllers, both SCSI and IDE/ATA, and also most software RAID solutions
    For More info on RAID 0+1 or RAID 10, RAID1+5 or RAID 15.
    If you do decide that RAID is a good option, make sure you use a quality RAID controller. Software RAID controllers are not good quality since they lower performance!

  2. Reeltoreelguy
    December 14, 2011 at 6:37 am

    FIDELIS--- Thanks for the info. My board has 2 ide connectors, one near the edge of the board and one next to it. The EDGE connector is used for one or two hard drives. The INSIDE connector is used for one or two opticals. I  do not know if the connections can be reversed. All drives are set to CABLE SELECT. I use 2 opticals and 1 hard drive as MASTER or SINGLE. If I understand you my original thinking is correct. A choice as to which hard drive to install the OS on, and a second choice as to which drive to use for subsequent downloads, either or both. Please confirm or correct that thinking.

      December 15, 2011 at 12:40 am

      Yes, you got it.  Make sure to connect the hard drives to the primary IDE connector and the cd/dvd drives to the secondary IDE connector.  Just as a note, it is not a good idea to connect a hard drive and a cd/dvd drive in the same ribbon.  The connections can be changed to use primary and secondary.  It is just a matter of changing the pin configuration in the back.  If you check the back of your hard drives, there is a plastic plug connected to a set of pins, it is just a matter of moving that pin according to the configuration explanation in the drive.

      Like I said before, the hard drive should explain how to connect the drive to make it primary, secondary or cable select.  If you decide to change the drive configuration to primary/secondary, make sure to set one drive as primary and another one as not make them both primary or secondary.  If cable select is working ok for you, don't change it.  Let me know if you have more questions or something is unclear.

    December 13, 2011 at 10:24 pm

    Hello, also if your drives are IDE, your primary disk will be assigned according to how the plug in the back of the drive is set.  With IDE configuration, a drive can be set as primary, secondary, or as cable select.  If your drives are IDE, they should have a description on the top of the drive letting you know how to set the plug to make a drive primary or secondary. 

    There should also be a primary and secondary channel for connecting hard drives and cd/dvd drives.  Usually the primary channel is used for setting your hard drives and the secondary channel for setting your cd/dvd drives.  If you have a ribbon that can acommodate more than one drive, there is two connections.  One connection is for primary drive and the second is for the secondary drive.  If you have this configuration make sure to set one drive as primary and the other as secondary by changing the plug.  If you use cable select, the primary drive will be assigned to the drive that is connected to the primary plug...and the secondary will be assigned to the drive that is connected to the secondary plug. 

    If you are using SATA drives, this doesn't apply.  When installing the operating system, you select the drive where your operating system will be installed and by default that will be your default start up drive.  You can change to the other drive in BIOS, but it will cause problems if there is no operating system on the drive.

    • Reeltoreelguy
      December 16, 2011 at 7:38 pm

      Thanks for verifying my thinking. I bought some 80 gig drives as I only have one 40. So I cant experiment. When I come across another 40 I will try it on my TEST BED. I will tell you the results when I take it on. Dont hold your breath.

      • Mike
        December 16, 2011 at 8:27 pm

        In case you bought/use IDE drives I suggest to take a look at the upgrade costs next time.

        IDE is dead - those drives are no longer produced. At this moment you pay about $100 for an 80GB IDE drive. 
        For that money you can easily get an inexpensive 1x or 2x Port SATA Controller plus a 250-500GB SATA hard drive.

  4. Mike
    December 13, 2011 at 5:11 pm

    Since you refer to drive "C" I assume you are going to install Windows:

    During the installation Windows will show you both drives separately and allow you to select on which one you want to install the operating system.

    I'm not sure what you mean by making the drive primary/secondary. The second hard drive will simply be listed as that ~ a second hard drive. Of course you can give it drive letter "x" or any other one (except "A" and "B" which are reserved for floppy drives).

    As for storing the downloads it's simply a matter of selecting the download location.

    If you want the drives to be combined to one 80GB you will need a motherboard or controller that supports RAID configuration.
    You can either set it up as a RAID 0 (which I personally don't suggest if you don't have enterprise/RAID hard drives) or if supported as a SPAN volume.

    Theoretically you can also create a SPAN volume using Windows by converting the hard drive into a "Dynamic Disk" however as a boot volume this is only supported by Windows XP Professional or later and I'm actually not sure if you can create that setup during installation.

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