Why is my C: drive on Disk1 and E: on Disk0 and is that bad?

Tony More January 19, 2013
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My Windows 7 system seems to be working just fine. I have two physical hard drives. One I use mainly for my OS and software, while the second drive is exclusively for data.

I was nosing around the Disk Management utility and was kind of surprised to see that my C: drive is on disk channel #1 (Disk1) and my E: drive (the one with my data) is on disk channel #0 (Disk0).

I’m wondering two things: (1) How did that happen, and (2) Does it make any difference?

I’m guessing it’s simply a matter of the SATA connectors I’m connected to. But I’m still wondering whether any experts think this somehow makes a difference with Disk0 not being the boot disk.

Thanks, folks!

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  1. Tony More
    January 21, 2013 at 3:41 am

    As I read everyone's replies and the Knowledge Base article, just as one replier indicated, perhaps it's a simple case of me attaching my drives to the SATA ports such that the boot drive was not Disk0. It's a little more complicated than that, though.

    After rebooting my system, I re-entered Disk Management. To my surprise, even though I made no changes to my system, I see the "channel assignments" have changed. Now my boot drive (C:) is Disk0 and my second hard drive is Disk1. Prior to rebooting, the channel assignments were reversed.

    I suppose I may have to re-read the Microsoft Knowledge Base article more thoroughly to get a better understanding of what's happening. As far as I can tell, this issue doesn't cause a problem insofar as the way my system works, but like the Knowledge Base article mentions, if both disks are the same size/type, you may have a hard time distinguishing one from the other.

    Thanks, everyone!

    • ha14
      January 21, 2013 at 5:09 pm

      great problem was solved, you did well thanks for informing makeuseof:)

  2. Tony More
    January 21, 2013 at 2:19 am

    Many thanks to all who've replied. I expected just some expert assurance. Instead, some of you, who are experienced/knowledgeable regarding this matter, ventured to go the extra mile by digging up the relevant Microsoft Knowledge Base article.

    Thank you again! I appreciate everyone's efforts.

  3. Oron Joffe
    January 19, 2013 at 3:34 pm

    It's eactly as you said Tony. You connected the system drive to the second SATA socket, and the data drive to the firsts. Generally speaking, this is just fine.
    If you had multiple *bootable* drives, the order in which they would be approached by the system would be the order of the SATA connectors, which could conceivably cause problems (particularly if you changed the connections at some point), but as things stand, everything's fine - leave your PC alone!

    • Tony More
      January 21, 2013 at 2:21 am

      Yes, you're correct, Oron. If all works well, then playing with something that's not broken only increases the risk of causing some new kind of problem. In the U.S., we have a saying: "If it's not broke, don't fix it." Thank you, sir!

  4. ha14
    January 19, 2013 at 12:46 pm

    if hard drive containing windows is not the first option in BIOS then simply you will not be able to boot windows.

    The disk drive numbers may not correspond as expected to the SATA channel numbers when you set up Windows Vista, Windows Server 2008, Windows Server 2008 R2, or Windows 7 on a computer that has multiple SATA or RAID disks
    http://support.microsoft.com/kb/937251

    • Paul Pruitt
      January 19, 2013 at 4:26 pm

      This is a great article by Microsoft and the explanation behind it is: "Microsoft has confirmed that this problem is due to design limitations in the Microsoft products that are listed in the "Applies to" section. This problem occurs because drives are enumerated in the order in which they are presented to the operation system by the system BIOS." And so it earlier explains: "The disk-assignment numbers may not necessarily match the corresponding SATA or RAID channel numbers. There is no assurance of a consistent relationship between PnP enumeration and the order of the hard disks that are detected during setup. Devices are presented in the order in which they are enumerated. Therefore, the disk-assignment numbers may change between startups. For example, assume that you run Windows Vista, Windows Server 2008, Windows Server 2008 R2, or Windows 7 Setup on a computer that has two unformatted SATA or RAID hard disks. In this situation, Windows may present the second hard disk as Disk 0 when you are prompted for the disk on which to install Windows Vista, Windows Server 2008, Windows Server 2008 R2, or Windows 7."

      Technically speaking, I'm not sure about "if hard drive containing windows is not the first option in BIOS then simply you will not be able to boot windows."

      If you go to the Boot Order in the BIOS and say you E drive is listed first and it doesn't have an OS on it; your CD/DVD player is listed next and there is not OS install disk in the player; your USB input is listed third; and your C: drive with the OS is listed 4th, the BIOS will just skip over the first three and boot from your C: drive no issue.

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