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Difference between MBR and GPT

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Difference between MBR and GPT
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In computer, a system has at least one hard drive for storing data. The physical drive is not able to store data directly without the creation of a partition in the storage. A partition is basically a section of the hard drive. The operating system treats this section as a separate logical volume.

A hard drive may be partitioned into multiple sections. Operating systems such as Windows and Linux may need more than one partition. But a partition cannot store data if there is no file system. So the partitions are formatted using NTFS and FAT file systems. Along with this, partitions are made according to structures called MBR and GPT.

What is MBR?

MBR stands for Master Boot Record. It is a piece of information stored in the hard disk that contains the code for starting or booting a computer. It is also called master partition boot sector and master boot lock. It is used to identify where the operating system is located and how the OS will be located.

It is also referred to as master partition sector as it contains a table that has the information about the partitions of the hard disk. MBR has a program that reads the partition’s boot sector record. This partition may contain the operating system that has to be booted into the RAM.

When you partition a hard drive, an MBR is created. But the partition does not have it. So, storage devices such as floppy disks do not have an MBR. To be specific, the MBR is located in the first sector of the hard disk.

The exact address of the Master Boot Record is Cylinder: 0, Head: 0, Sector: 1.

The MBR was introduced in 1983 along with PC DOS 2.0. It contains the boot loader for the installed operating system such as Windows. It also has information regarding the logical partitions of the hard drive.

MBR has three primary components:

  • Master partition table
  • Master boot code
  • Disk signature

The working process of the MBR is as follows:

  • As soon as you turn on the computer, the BIOS (Basic Input Output System) looks for a target device from which it can boot. This device must contain the master boot record.
  • After the master boot code is found, MBR looks for the Volume boot code of the partition. This will tell the location of the system partition.
  • Then the system partition’s boot sector is used to initialise the operating system.
  • The MBR can be affected by boot sector viruses. Viruses such as Stoned Empire Monkey can harm the MBR and leave it unusable. This may stop the operating system from booting.

What is GPT?

GPT stands for GUID partition table. It is a part of the UEFI (Unified Extensive Firmware Interface) standard that is used to describe the layout of the partition table within the hard drive. The UEFI is actually a type of software specification that is used to connect the system’s operating system and the firmware.

GPT has a unique identifier for every partition called GUID. This is a random string that identifies each partition.

The GPT is used for replacing the MBR that is in a system’s BIOS. Although it is part of the UEFI standard, it can also be used with old BIOS-based systems. It was introduced primarily as an enhancement of MBR. This is because MBR can only support a partition size of less than 2 TB. Therefore, GPT offers a more flexible system of partitioning.

Nowadays most operating systems support GPT. Operating systems such as Windows and Mac OS X can only be booted from GPT partitions.

GPT stores its boot data and partitioning data across disks. So, the system is more robust and there are fewer possibilities of this data to be lost or be corrupted.

Another important feature GPT has it maintains the correctness of data. It stores CRC (Cyclic Redundancy Check) values. CRC is an error-detecting code that is used for identifying accidental changes made to data. So, if some data gets damaged, GPT can recover or fix it. It might try to recover the data from another location on the disk.

GPT vs MBR

Basis of comparison

MBR

GPT

Partitions supported

As it has a 64-byte partition table, up to 4 primary partitions can be supported where each partition will be of 16 bytes. If another partition is required, the fourth partition can be used to create an extended partition. In this extension, a maximum of 128 sub-partitions can be created.   

Up to 128 partitions are supported where each one is 128 bytes in size. Here the extended partition need not be used and the more partitions can be made.

Partition size

The maximum disk size supported is of 2 TB. In an MBR disk, a length of 4 bytes is used for a partition. So the maximum value is of  4,294,967,295 sectors. Each sector is not more than 512 bytes, so the maximum size is of 2 TB.   

A length of 8 bytes is used for a partition here. The maximum partition size supported is 9.4 ZB.

Support for Firmware interface

BIOS

UEFI

Operating system support

Operating systems such as Windows 7 and older systems such as Windows XP, 95 and 98 support MBR.

Modern operating systems such as Windows 10, 8.1, 7and Vista.   

Data integrity  

Here, the partition and boot data is stored in a single section of the partition. There is no checking of the correctness of data. If there is some problem, the operating system might go down   

Data is stored in boot and partition data in the disk. The data integrity is checked using a cyclic redundancy check.

Conclusion

You know that MBR is the old partitioning method whereas GPT is a modern method. GPT has many advantages such as partition size, techniques for protecting data integrity and disk size. So, if you are looking to enjoy these facilities – GPT is the best for you.

But on the other hand, there are many systems all over the world that still use MBR. Operating systems such as Windows XP and Vista utilize MBR for partitioning. So, if you are working on an older system that does not support UEFI, it will only support GPT and not MBR.

At the end of the day, the partitioning system that will suit your needs will depend upon the technology and operating system you are using.