Can't format 3TB drive with GPT


I just put together a system with two 3TB Western Digital Caviar Green hard drives and an ASRock 79 Extreme 6/GB mobo. When I install Win 7, it will only format 2TB. The bios has UEFI and when I check the BIOS, the WDC drive and Bluray burner are shown as AHCI devices.

Things have changed some since the last time I built a system.

Do you think I need to flash the BIOS? Or, how do I get this thing to recognize a 3TB drive?
14 answers Last reply Best Answer
More about format drive
  1. Any chance you are trying to install a 32bit version of Win 7?
  2. It is definitely Win 7 Professional 64 bit. Says so on the disk. :pt1cable:
  3. Best answer
    Try this link:

    Please ensure that you do have the most up-to-date Bios installed prior to commencing with the install.
  4. When you have an EFI system on your MB, you have to choose between MBR and GPT as the partition style before partitioning it. You can't go back and change one to the other later without starting all over.

    You can tell what partition style your HDD is using by going to Disk Management, right click on the Disk Info block, clicking on Properties, then the Volume Tab. It will say, MBR, or GPT.

    If it's MBR, it can only address 2.2TB of address space. Using a Basic Disk (not Dynamic) type, it has to be GPT to address over the 32 bit limit.
  5. Here's what ASRock Support said -

    Due to Microsoft OS limitation the drive larger than 2 TB will automatically divided by 2 partitions and first partition is 2 TB.

    GPT only works on non –OS drive.

    For more detail about the issue, please contact the Microsoft.

    Thank you

    That's basically what the Win 7 installation software is telling me - it set aside a 100MB partition for system files and will let you create additional partitions up to 2047.9 gig = 2TB

    The install software won't let me create a new partition with the remaining space which it shows as 746.5 GB. Apparently you can't format a 3TB partition on the drive you are installing Win 7 to and you end up losing a gig of storage space.

    Anyone disagree?
  6. Hello again.

    Well, you can use a GPT style partition for the OS, you just have to choose it initially. In a few years, GPT partitions will be the "standard" in that it is 64 bit, so can address ~ 18EB. WD and Seagate's are set up to use the 2.2TB + 800GB separate drives, I think the Hitachi's will give you a 3TB partition, but not 100% sure.

    And of course, if you set the system up to use Dynamic Drives, or convert from a basic to a dynamic drive type, you can span both disks into a single large 3TB volume.

    Check the properties on the Disk as mentioned earlier to see if you set your partition style up as MBR, as compared to GPT.
  7. I found the answer, I Googled the error I got when I tried to create a new partition beyond 2TB and found this -->

    That's not the whole story (doesn't it seem like that's always the case). The rest of the info was in the article that ELMO_2006 Posted above -->

    1) In BIOS/UEFI set the 1st drive to UEFI even though nothing is there (it makes a difference, I tried it without doing this and got an error)
    2) Set your optical drive with Win 7 CD as #2 boot drive
    3) Run Win 7 install and when you get to the initial screen, hit Shift - F10
    4) Run diskpart.exe
    5) Before you run "convert gpt", use the "clean" command to remove any data and configuration files. I assume if it's a new disk this won't be necessary. Do it anyway just to be sure there aren't system files on there.
    6) "exit" 2 times and start the Win 7 install program
    7) Run Custom Install - Advanced Options and it will show one 2.8 TB partition.
    8) Select "new" and it will create 2 systems partitions and one new partition that is 2.7 TB
    9) Only format the 2.7 TB partition, the other 2 were already formatted when Windows created them. If you format them, you will remove the system files that Windows put on them and you will get an error on installation.

    When I didn't use the "clean" command, Windows reverted back to the MBR set up and gave me an error saying the drive must be GPT not MBR. Even though I ran the "list" command and it showed that the drive was a GPT drive, it still reverted back to MBR. I assume it did this because there was still data/configuration files on the drive from the system files Win 7 added when I was trying to format the drive prior to setting it to GPT.

    And......there it is in My Computer, a 2.72 TB C: drive.

    And ..... there it is in Disk Managment a 2794.3 GB drive with a status of - Healthy (EFI System Partition), thanks to John_Vankirk above I knew how to get there.

    1) Click the Windows start button (lower left screen), enter "command" in the "Search programs and files" search box
    2)Enter diskpart.exe
    3) Enter "list disk"
    And.......there it is, a 2.794 TB Disk 0 with the GPT column checked

    And it's all working and it's screamin' fast. Don't you just love the world of modern automation?!!! When it works that is.... ;)
  8. Thanks everybody!

    I gotta say - this is the 1st time I've been on this forum and I'm impressed. I got answers faster than if I could have called tech support (and you saw the quality of tech support's e-mail answer above that I waited a day for), if there was any such thing. On a different post, I was writing a comment to ask another question - when I posted the question, someone had already posted ahead of me with the answer.

    Good show!

    I hope I can help you too someday.
  9. John_VanKirk said:
    Hello again.

    Well, you can use a GPT style partition for the OS, you just have to choose it initially.

    Hi John,

    The problem was the Win 7 installer didn't give me that option and I didn't have another system I could format the drive on.

    Your info was part of the solution and I thank you for that. I hope I can help you some day.
  10. Best answer selected by skydoggie77.
  11. That's the nice thing about Tom's Hardware, you can ask a question, get the info you need to delve deeper into one aspect of computer science, and in short order, you have become an expert in one area to help others. All of us have asked the same questions at some point.

    You are looking into the changing standards of disk types, partition styles, addressing by the OS, BIOS, HDD firmware, which is very confusing at present. It's really basic to data storage, but understood by very few people.
  12. John_VanKirk said:

    You are looking into the changing standards of disk types, partition styles, addressing by the OS, BIOS, HDD firmware, which is very confusing at present. It's really basic to data storage, but understood by very few people.

    Hi John,

    I was thinking about that last night. I had forgotten how quickly technology changes and that when you're buying systems that are on the forward edge of the technology, there are a lot of new standards that people don't understand yet. Even the motherboard manufacturer didn't know how to format a 3TB UEFI partition. But, this was much easier than in the old days because of information sites like this. There used to lots and lots of trial and error and trips back and forth to Fry's Electronics to ask questions.

    The last time I built a system, AGP was the graphics card standard. A lot has changed and is it ever fast! Gotta love that. Now if I can just keep the CPU cool. I'm going to get one of those liquid coolers., and then.......

    Thanks once again.

  13. skydoggie

    Thanks for the post/ It helped after 2 days of trying to figure out how to do this on my new Asus z87 plus mobo.
    The one step no one mentions is that after you perform the diskparting and the clean, when you get back to the Windows set up screen you expect the 3 partitions to show up. They won't until you pick drive options and then press NEW. Windows will inform you that it needs to spread this out over 3 partitions and ask you if it is Okay. Then the 3 gbt partitions will show up. Not unitl you press new under drive options will the partitions be created. Took me two days to figure this out!!

  14. in my system I have a 250 gb hard drive where windows is installed. If I go on an put a 3TB as a secondairy drive, I will have access to the 3TB completely?
    Or I would have to create two partitons?
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