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2TB Drive Limit in Win7?

Discussion in 'General Software' started by bokou, Mar 10, 2011.

  1. bokou

    bokou New Member

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    Friend of mine is running two 1.5tb drives in raid and theoretically should have 3tb available (well, close to it...). However Win7 only shows 2 available TB even though the bios shows all 3 available. I asked if he has SP1 installed and he said yes.

    We're kind of stumped... any suggestions?
     
  2. crazyeyesreaper

    crazyeyesreaper Chief Broken Rig

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    herp derp boot drive cannot be larger then 2TB you now have your answer
     
  3. bokou

    bokou New Member

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    oh no shit... did not know that. Now I guess I do!! Thanks! That's a built-in windows limitation? Is it an artificial limitation or more or less like the 3gb RAM limitation we had to just deal with with 32-bit win?
     
  4. sneekypeet

    sneekypeet Unpaid Babysitter Staff Member

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    Bios limitation, I guess the newer EFI bios' wont have this limitation.
     
  5. Mike0409

    Mike0409

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    Its a BIOS Limitation of MBR. Windows 7 allows the format of GPT which supports over 1.5-2TB HD's.
     
  6. Sasqui

    Sasqui

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    What is GPT?

    BTW... I just learned something by passing through this thread!
     
  7. newtekie1

    newtekie1 Semi-Retired Folder

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    Correct, the BIOS requires a MBR(Master Boot Record) on the disk for it to boot from it. So the drive has to be formatted as an MBR disk, which has a limit of 2TB. You can format the drive as GPT(GUID Partition Table) but then the BIOS can't boot from it because it has no MBR.

    I'm not sure if EFI BIOSes fix this issue or not.
     
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  8. Mike0409

    Mike0409

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    GPT is a file system that supports over 2TB. It was implemented in Server OS's a while back but never setup on Windows XP due to 2TB being more than enough space at the time. I believe they made it live in Vista SP1 and then just continued supporting it in Windows 7.


    Wiki on GPT http://en.wikipedia.org/wiki/GUID_Partition_Table
     
  9. JrRacinFan

    JrRacinFan Served 5k and counting ...

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    GUID Partition Table.

    It's moreless a controller limitation and not actually a bios limitation. Currently only raid controllers AFAIK on the market that can do GPT raid arrays are onboard with an efi bios, aka Sandy bridge.

    EDIT:

    Damn you guys are fast!
     
  10. newtekie1

    newtekie1 Semi-Retired Folder

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    The controller doesn't play much part in it at all. All the controller handles is the array, GPT/MBR is decided by the OS. My RocketRAID 2300 handles my GPT array just fine, to the controller it looks like any other RAID array, it doesn't care how the drive is formatted.

    It just comes down to the BIOS actually being able to boot off a GPT drive, and I think EFI allows that, but I'm not sure.
     
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  11. Mike0409

    Mike0409

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    Correct on that. EFI does support GPT booting.

    GPT is only needed with 2TB or higher. And with RAID and other setups you still need to partition it correctly with Virtual drives, this is even present with Server 2008 on boards that dont have an EFI BIOS.
     
  12. JrRacinFan

    JrRacinFan Served 5k and counting ...

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    But with that said, if the controller can set it as boot, and windows 7 supports GPT, then how can the conventional non-EFI bios control how the raid controller boots then? That's the link where I am lost at ....

    I mean, what's a raid controller for if it can't control the raid array its attached to "?"
     
  13. Frick

    Frick Fishfaced Nincompoop

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    I think Mac uses GPT, so EFI supports it.
     
  14. Mike0409

    Mike0409

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    The controller is still controlling the RAID, it all depends on how the drives are partitioned/formatted.

    Like in the OP scenario - 2-1.5TB drives - should be 3TB of space. So you setup a RAID 0 using your controller, and boot into Windows (Or go to install Windows) You need to create 1 Partition for OS (For the MBR record for Windows), and the rest as a secondary GPT partition (Once windows is installed) As a 2nd Virtual Disk.

    EDIT: So it would look like the following.

    C: - OS 100GB
    D: - DATA 2.7TB
     
  15. JrRacinFan

    JrRacinFan Served 5k and counting ...

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    Ok so then it is an OS limitation, not necessarily bios.... Unless I am reading that wrong.
     
  16. Frick

    Frick Fishfaced Nincompoop

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    You're reading it wrong (unless I'M reading it wrong :p). The 2TB+ partition would be GPT and the smaller OS one would be MBR.
     
  17. JrRacinFan

    JrRacinFan Served 5k and counting ...

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    Let me rephrase from my previous post: Meaning one big GPT RAID 0 volume is not bootable, still rendering it an OS limitation. Not necessarily bios/efi, not necessarily controller.
     
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  18. newtekie1

    newtekie1 Semi-Retired Folder

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    No, not a OS limit at all.

    When the BIOS checks for boot devices it looks for a MBR on each disk, if it can't find it, it labels the disk non-bootable and moves on to the next disk in the boot priority. Because a GPT disk does not have a MBR, the BIOS marks it as non-bootable. This has nothing to do with the OS, this is a BIOS limitation. The BIOS doesn't know how to read a GPT drive as bootable and start the boot process from a GPT disk. EFI, appearently, does know how to read a GPT disk as bootable and can start the boot process from a GPT disk.

    In the case of a RAID array, even if the RAID controller labels the drive as a bootable drive, if the BIOS doesn't find an MBR, the BIOS won't be able to boot from it.

    Also, AFAIK, you can not have a MBR partition and a GPT partition on the same drive. The entire drive has to be one or the other.
     
    Last edited: Mar 10, 2011
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  19. JrRacinFan

    JrRacinFan Served 5k and counting ...

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    Oh ok that's where I had the misconception, I thought the raid controller was doing the actual booting.
     
  20. Frick

    Frick Fishfaced Nincompoop

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    Just want to point out that Windows XP 32bit can not read GPT disks. 64 bit can though.

    So if you're on Windows XP and buy one of them external drives saying "For Mac" there's no point in buying unless you have another system handy and can change it.
     

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