The Differences Between MBR and GPT

If you have dabbled with your hard disk and is always doing formatting and partitioning, you will surely come across the term “MBR” and “GPT”. This is especially evident when you are dual-booting your Mac and faced with the problem of having to switch from GPT to MBR. You probably are wondering, what are the differences between MBR and GPT and is there any benefit using one over the other? We wil clear your doubt in this article.

You probably know that you can split your hard disk into several partitions. The question is, how does the OS know the partition structure of the hard disk? That information has to come from some where. This is where MBR (Master Boot Record) and GPT (Guid Partition Table) come into play. While both are architecturally different, both play the same role in governing and provide information for the partitions in the hard disk.

MBR is the old standard for managing the partition in the hard disk, and it is still being used extensively by many people. The MBR resides at the very beginning of the hard disk and it holds the information on how the logical partitions are organized in the storage device. In addition, the MBR also contains executable code that can scan the partitions for the active OS and load up the boot up code/procedure for the OS.

For a MBR disk, you can only have four primary partitions. To create more partitions, you can set the fourth partition as the extended partition and you will be able to create more sub-partitions (or logical drives) within it. As MBR uses 32-bit to record the partition, each partition can only go up to a maximum of 2TB in size. This is how a typical MBR disk layout looks like:

mbr-disk-layout

There are several pitfalls with MBR. First of all, you can only have 4 partitions in the hard disk and each partition is limited to only 2TB in size. This is not going to work well with hard disk of big storage space, say 100TB. Secondly, the MBR is the only place that holds the partition information. If it ever get corrupted (and yes, it can get corrupted very easily), the entire hard disk is unreadable.

GPT is the latest standard for laying out the partitions of a hard disk. It makes use of globally unique identifiers (GUID) to define the partition and it is part of the UEFI standard. This means that on a UEFI-based system (which is required for Windows 8 Secure Boot feature), it is a must to use GPT. With GPT, you can create theoretically unlimited partitions on the hard disk, even though it is generally restricted to 128 partitions by most OSes. Unlike MBR that limits each partition to only 2TB in size, each partition in GPT can hold up to 2^64 blocks in length (as it is using 64-bit), which is equivalent to 9.44ZB for a 512-byte block (1 ZB is 1 billion terabytes). In Microsoft Windows, that size is limited to 256TB.

gpt-partition-scheme

From the GPT Table Scheme diagram above, you can see that there is a primary GPT at the beginning of the hard disk and a secondary GPT at the end. This is what makes GPT more useful than MBR. GPT stores a backup header and partition table at the end of the disk so it can be recovered if the primary tables are corrupted. It also carry out CRC32 checksums to detect errors and corruption of the header and partition table.

You can also see that there is a protective MBR at the first sector of the hard disk. Such hybrid setup is to allow a BIOS-based system to boot from a GPT disk using a boot loader stored in the protective MBR’s code area. In addition, it protects the GPT disk from damage by GPT-unaware disk utilties.

OS Support

Intel Macs are using GPT by default and you won’t be able to install Mac OS X (without tweaks and hacks) on a MBR system. Mac OS X will run on MBR disk though, it is just that you won’t be able to install on it.

Most Linux kernels come with support for GPT. Unless you are compiling your own kernel and you didn’t add this feature in, you should have no problem getting your favorite distro to work in GPT disk. One thing to note, you wil have to use Grub 2 as the bootloader.

For Windows, only the 64-bit version of Windows from XP onward support booting from GPT disk. If you are getting a laptop pre-installed with 64-bit Windows 8, most probably it is using GPT. For Windows 7 and earlier version, the default configuration will be MBR instead of GPT.

In most cases, you will be fine with either MBR or GPT. It is only in situation where you need to install Windows on a Mac, or when you need to have a partition bigger than 2TB, that you need to use GPT, or convert MBR to GPT. Also, for the newer model of computer that uses UEFI, it will only support GPT.

If you have any question, feel free to ask in the comments below and we will be around to answer your question.

39 comments

  1. One thing to note, you wil have to use Grub 2 as the bootloader.

    This is not true. You can use a boot manager like rEFInd or gummiboot and use the kernel’s EFISTUB loader to boot, providing your kernel has that option enabled: `CONFIG_EFI_STUB=y`.

    • @Ed, Thanks for pointing it out. I should have mentioned that Grub 2 (as compared to Grub legacy) should be used as grub legacy doesn’t have direct support for GPT. It can, however, be achieved through some hacks and recompilation, but not everyone want to go that path.

  2. I am really no expert in this field and I have the following question: If I purchase a brand new hard drive, how do I know if it supports the MBR or the GPT scheme?

    • Whether the computer supports MBR or GPT does not depend on the hard disk. It depends on the BIOS and the OS. This means that when you purchase a new hard drive, you can format it to either MBR or GPT, depending on your computer and what your needs are.

  3. Thanks for the article.
    I am using windows xp 32bit, if I format my “c” drive and install 64bit can I get GPT instead of MBR? And how can I know that what kind’s of boot record any computer have?

    • Formatting your hard disk, or installing 64-bit Windows won’t convert it from MBR to GPT. In Windows 7 and above, you can easily convert MBR to GPT without wiping your data (via the Disk Management application).

      Since you are running Windows XP 32-bit, you are definitely using MBR. It is not necessary to convert to GPT unless you are restricted by its limitation.

  4. I came into this problem MBR and GPT issue while trying to install Linux 8 on my 32 bit Win 7 laptop, It tells me that the disk was originally contained a primary and altrnative GUID partition tables but the protective MBR is invalid.
    It goes on to mention that a legacy tool was used to change the partition table stored in the MBR….
    Which way do I go to be able to achieve dual boot btw win 7 and Linux without hassles?
    Thanks

    • In this case, you might want to recreate the partition table using tool such as GParted. Then you can format the hard disk and split it into the various partitions for Windows and Linux.

  5. I purchase a new laptop hard drive of segate 500GB & if i install windows 7,windows is loading ant then i click to install now,then setup is preparingthen open a new box where show the hard disk space but box is blank& there are no any driver shows . plz help me how to install windows 7 in my laptop.send clear information to gtsranjeet@gmail.com

  6. I want to change GPT to MBR, can i change?? (win 8 64bit)
    reason to change: i want to install win 7(want use both win 7 and win 8 64bit) when i chose any partition in installation process, a error occurred ” partition is in GPT mode”

  7. I live in Serbia. I bought Asus Notebook with preinstalled Windows 8 x64. I am using Norton Ghost from Hiren ‘s Boot CD to make image a hard drive, but something I’m broke and my Windows will not start, search the installation disk to perform the repair., But when you do the work, again asking for the same repair. Doubt that I Corrupt MBR or GPT. i do not know which system is followed in my HDD. How to find out whether the MBR or GPT and how to try to fix it. Thank you in advance for your help

    • I don’t think the issue lies with the MBR or GPT. You might want to reformat the hard disk with a Windows 8 DVD.

  8. You people, including the author of this page, use the word HACK carelessly. Tweak or Tweaking, is expressed as to making changes/adjustments as in tuning something to fit your required needs. Hack or Hacking is expressed typically as to entering into a file/system that is encrypted through by means of using various methods or entering into a file/system by means of manipulation/exploitation due to poor integrity of such file/system. In fact, there are many people on the web who use these words interchangeable when they are not the same meaning.

    ADG

    • Wow, feisty. I think you will find that there is some debate about the usage of the word ‘hack’, and through common (and sometimes incorrect) usage it has expanded to include a number of uses quite distinct from the earliest uses of the word. The earliest uses, by the way, can be traced (or have been argued) to be mainly two camps – a technically adept computer/technology user (e.g. coder), or someone subverting systems as you described above, in the earliest cases phone phreaks.

      http://en.wikipedia.org/wiki/Hacker_definition_controversy#Hacker_definition_controversy

      It’s more than acceptable to use it in the sense of someone ‘hacking’ some code together, or ‘hacking’ into a computer system as you describe, either on a white-hat or black-hat basis, or indeed ‘hacking’ something in the sense of tweaks and modifications to either the original intended use or to the core system itself – e.g. getting MacOS to run on standard Intel PC hardware.

      So in fact, the usage of the word ‘hack’ in this article is not careless at all.

  9. I have an external HD that cannot be mounted but it turns on when I plug it. I’m guessing the partition structure data has been corrupted. How do I know which one it is so that I can format it accordingly and be able to recover my data. Thanks!

    • I am guessing that you are using Windows. When you format it, it will erase all your data as well, how are you going to recover your data? You might want to boot up your computer with a Linux live CD. Mount the external HD in and it should be detected and mounted.

  10. Can a GPT based disk be added to a Win 7 system using a MBR based disk in a dual boot configuration where the boot disk is selected at start up or BIOS default settings? I want to isolate the Linux and BSD OS’s on the GPT disk using GRUB 2 to select the OS to be loaded. Win 7 will never be booted from the GPT drive nor any Linux distribution loaded from the MBR drive.

  11. I bought a 240gb ssd and was wondering should i use MBR or GPT. I am using vista 32 but want to upgrade to win 7 32.

  12. I was attempting to load OSX (hackintosh) on my PC laptop with no luck. If I changed my HDD from MBR to GPT would that help?

  13. Just bought an external drive with 4TB. Should I convert the drive to GPT in order to use the entire 4TB space on the drive? Thanks.

  14. I think “you can only have 4 partitions in the hard disk ” should be “you can only have 4 PRIMARY partitions in the hard disk”. I can split the extended partitions to many as I want, right!

  15. If you are using windows you can use the command “diskpart” and switch the partition of your hard disk or thumb drive (pen drive) from MBR GPT . No need to install anything if you are under Winslows.

    • insert windows dvd and start installation and choose custom installation.

      don’t do anything, press shift+f10 a dos shell will open

      type diskpart and then then type list disk, finally type select disk “x”

      enter clean if you need to clear the partition otherwise type convert to gpt

  16. I am using Mac and my Hard drive is presently has one partitioned to GPT / Mac OS extended (Journaled )
    Now that i need my 1TB WD my pass port ultra to be able to read and write form Mac as well as windows OS pc
    and need a pass word protection which WD has builtin or can be downloaded,i want my HD to be single partition and use only WD Security Lock soft ware for pass word protection , and formate it for both OS useable,
    plz help me how do i partition my WD 1 tb my pass port ultra for useable to mac and OS at the same time can use to lock my HD using WD security lock
    regards
    Hamim

  17. I tried installing windows 8.1 but it says that my partition is in MBR and needs to be converted to GPT. My questions are:
    If I do that will all my data be wiped because i can’t turn my windows on as some files got corrupt.
    Is it possible to install Windows XP then backup my hard drive then switch to GPT and create partitions again, then install windows 8.1? Will it work?

    • The easiest way is to download Ubuntu ISO and create a live USB. Boot into
      the live USB and you will be able to access your hard disk. From there, you
      can backup your data. Once you are done, you can proceed to install Windows
      8.1

  18. I need help. I just got a new mother board, cpu AMD 3.6, memory 8 gig, and video card. My problem is that windows 7 will not work and I can not install windows 8 because it says my disk mrb and I need to have GTP. What exactly do I need to do seeing as nothing boots up except bios.

    Any pointers would be great. I just want the stupid thing to run. I have two system partitions and two drive partitions.

  19. Thats kind if the same problem that im having. I just want to make sure i have this right before i do anything else. I have windows 7 installed on a solid state and i want to use a 4tb hard drive for storage. So tell me if im right, unless you have uefi your not going to be able to get the full hard drive space but if you partition with gpt you can.

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