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Thread: Partition larger than 2 TB?

  1. #1
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    Partition larger than 2 TB?

    Hello,

    On a Ubuntu 11.04 x64 Server with a 6 TB raid array I am experiencing something strange.

    Once i enter fdisk using

    Code:
    fdisk /dev/sdb
    and create a partition, then the maximum number of blocks I can have, equals to 2 TB of disk space.

    Does this mean, that I can't create a partition larger than 2 TB?

    I also tried creating another partition, however the maximum number of blocks on the second partition equaled to 1,5 TB.
    Creating a third partition was weird - although choosing the last block of the second partition as the starting block, and the maximum block as ending block, the partition showed, when fdisk was issued p, that the block range was within the other partitions?!

    Am I doing something wrong trying to partition the disk, or should I split the raid array into 3x 2 TB raid arrays instead?


    Generally I don't see the point why a partition should be limited to such small an amount as 2 TB?

    Hope someone has a clue.

    Thanks.

  2. #2
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    Re: Partition larger than 2 TB?

    What partition table are you using on the disk/array? MBR is limited to 2TiB partitions. GPT, however, has no such limit, as far as I am aware.
    http://xkcd.com/293/
    There are 10 kinds of people in this world: Those who understand ternary, those who don't, and those who confuse it with binary.

  3. #3
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    Re: Partition larger than 2 TB?

    Quote Originally Posted by WorMzy View Post
    What partition table are you using on the disk/array? MBR is limited to 2TiB partitions. GPT, however, has no such limit, as far as I am aware.
    How do I see what partition table I am using, and eventually change it?

  4. #4
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    Re: Partition larger than 2 TB?

    Code:
    sudo parted -l
    e.g.

    Code:
    wormzy@sakura[pts/1]:~$ sudo parted -l
    Model: ATA SAMSUNG HD103SJ (scsi)
    Disk /dev/sda: 1000GB
    Sector size (logical/physical): 512B/512B
    Partition Table: gpt
    
    Number  Start   End     Size   File system  Name  Flags
     1      1049kB  700GB   700GB  xfs
     2      700GB   1000GB  300GB  xfs
    
    
    Model: ATA SAMSUNG HD103UJ (scsi)
    Disk /dev/sdb: 1000GB
    Sector size (logical/physical): 512B/512B
    Partition Table: msdos
    
    Number  Start   End     Size    Type     File system  Flags
     1      32.3kB  1000GB  1000GB  primary  ntfs         boot
    msdos = MBR

    You can use parted to create new partition tables. This will show you how:
    http://www.cyberciti.biz/tips/fdisk-...eater-2tb.html
    Last edited by WorMzy; August 10th, 2011 at 09:45 PM.
    http://xkcd.com/293/
    There are 10 kinds of people in this world: Those who understand ternary, those who don't, and those who confuse it with binary.

  5. #5
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    Re: Partition larger than 2 TB?

    You can also use gdisk.

    GPT fdisk Tutorial -srs5694 in forums
    http://ubuntuforums.org/showthread.php?t=1439794
    http://www.rodsbooks.com/gdisk/


    I do not know enough about RAID to know if you need a bios_grub partition but would suspect you do.

    Since the BIOS Boot Partition ("bios_grub" flag set in GNU Parted) is used without a filesystem for storing GRUB 2 boot code "unknown" filesystem! may be shown in many Partition tools.

    However, in the GPT setup, there is no space following the 512-byte MBR for embedding the "second stage" core.img. Thus, you must make a separate "BIOS boot partition" to hold core.img. You can set bios_grub flag in gparted or with command line: In GPT fdisk (gdisk), give it a type code of EF02.
    BIOS Boot Partition of 1 MiB for partition alignment.
    For info on UEFI boot install & repair:
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to close thread when/if answered completely.







  6. #6
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    Re: Partition larger than 2 TB?

    Quote Originally Posted by WorMzy View Post
    Code:
    sudo parted -l
    e.g.

    Code:
    wormzy@sakura[pts/1]:~$ sudo parted -l
    Model: ATA SAMSUNG HD103SJ (scsi)
    Disk /dev/sda: 1000GB
    Sector size (logical/physical): 512B/512B
    Partition Table: gpt
    
    Number  Start   End     Size   File system  Name  Flags
     1      1049kB  700GB   700GB  xfs
     2      700GB   1000GB  300GB  xfs
    
    
    Model: ATA SAMSUNG HD103UJ (scsi)
    Disk /dev/sdb: 1000GB
    Sector size (logical/physical): 512B/512B
    Partition Table: msdos
    
    Number  Start   End     Size    Type     File system  Flags
     1      32.3kB  1000GB  1000GB  primary  ntfs         boot
    msdos = MBR

    You can use parted to create new partition tables. This will show you how:
    http://www.cyberciti.biz/tips/fdisk-...eater-2tb.html
    Is this guide correct, that I have to recompile the Linux kernel?

  7. #7
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    Re: Partition larger than 2 TB?

    Not sure about that. It's a four year old tutorial, so it may be out of date.

    Run
    Code:
    zgrep EFI_PARTITION /proc/config.gz
    and if it says
    Code:
    CONFIG_EFI_PARTITION=y
    Then you don't need to recompile the kernel.

    (I'm assuming the Ubuntu kernel has /proc/config.gz enabled)
    http://xkcd.com/293/
    There are 10 kinds of people in this world: Those who understand ternary, those who don't, and those who confuse it with binary.

  8. #8
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    Re: Partition larger than 2 TB?

    I have never compiled a kernel and have been using gpt with Maverick (BIOS system) since it was in beta.

    Some have posted about using UEFI to boot, while a few have it working there are some issues with grub2.
    For info on UEFI boot install & repair:
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to close thread when/if answered completely.







  9. #9
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    Re: Partition larger than 2 TB?

    The standard Linux fdisk utility works only on MBR disks and on some more exotic disk types, but not on GPT disks. Thus, from post #1 it's obvious that you're trying to create MBR partitions, not GPT partitions. To create or modify GPT partitions, you must use gdisk (an fdisk workalike) or a libparted-based tool (parted, GParted, etc.), as others have said.

    Since your initial example shows you working on /dev/sdb, it appears that you've got a true hardware RAID controller. With such a controller, you can treat the array as if it were a physical disk of that size, so you don't need to worry about some of the software RAID issues that can cause problems sometimes. If you're booting in BIOS mode, though, you'll need to create a ~1 MiB BIOS Boot Partition, as oldfred has said; and you'll need to ensure that your kernel falls below the 2 TiB mark. The most reliable way to do this is to create a separate /boot partition (which is entirely different from the BIOS Boot Partition) and put the /boot partition before the 2 TiB mark on the disk. If you've got a new motherboard with UEFI support, you should create a ~200-250MB EFI System Partition (ESP) instead of a BIOS Boot Partition. If you're not sure which you've got, you can create both partitions.

    You do not need to recompile an Ubuntu kernel to use GPT -- at least, not any recent version of Ubuntu. I've got several 11.04 installations on GPT disks with stock kernels and they're all fine.
    If I've suggested a solution to a problem and you're not the original poster, do not try my solution! Problems can seem similar but be different, and a good solution to one problem can make another worse. Post a new thread with your problem details.

  10. #10
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    Re: Partition larger than 2 TB?

    Quote Originally Posted by srs5694 View Post
    The standard Linux fdisk utility works only on MBR disks and on some more exotic disk types, but not on GPT disks. Thus, from post #1 it's obvious that you're trying to create MBR partitions, not GPT partitions. To create or modify GPT partitions, you must use gdisk (an fdisk workalike) or a libparted-based tool (parted, GParted, etc.), as others have said.

    Since your initial example shows you working on /dev/sdb, it appears that you've got a true hardware RAID controller. With such a controller, you can treat the array as if it were a physical disk of that size, so you don't need to worry about some of the software RAID issues that can cause problems sometimes. If you're booting in BIOS mode, though, you'll need to create a ~1 MiB BIOS Boot Partition, as oldfred has said; and you'll need to ensure that your kernel falls below the 2 TiB mark. The most reliable way to do this is to create a separate /boot partition (which is entirely different from the BIOS Boot Partition) and put the /boot partition before the 2 TiB mark on the disk. If you've got a new motherboard with UEFI support, you should create a ~200-250MB EFI System Partition (ESP) instead of a BIOS Boot Partition. If you're not sure which you've got, you can create both partitions.

    You do not need to recompile an Ubuntu kernel to use GPT -- at least, not any recent version of Ubuntu. I've got several 11.04 installations on GPT disks with stock kernels and they're all fine.
    Thank you, I'll try fooling around with GPT.
    Yes, it is a hardware raid controller in the server.

    I am getting kinda confused with the BIOS/EFI partition?
    As you might notice from /dev/sdb, I do have a partitioned and functioning /dev/sda which the system and kernel runs on. The 6 TB raid array (/dev/sdb) is for storage only, so do I need those at all?

    Thanks!

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