How can we define MBR?

[generalpy]

I was studying partitioning for Comptia A+ using Mike Meyers' course and I am stuck on MBR. So how can we define MBR? Is it a partition type or is it a partition itself?

[Eigenvektor]

The master boot record is a specific sector of the disk that is read by the BIOS/UEFI to determine where to boot from.

 

So it's not a partition as such, nor is it tied to any partition. It's simply a well defined region of the disk where boot records are located.

[SupaKomputa]

AFAIK MBR is a boot sector (some call it boot loader), it's not a partition type which like fat32, ntfs, hfs+ etc.

It sorta like a receptionist at a hotel, which has all the rooms inventory (partitions) and your room location (bootable OS).

MBR has a limit of 2TB of a single partition with maximum of 4 primary partitions, GPT solved this problem by allowing infinite number of partitions (as high as the OS allows) with no size restrictions.

[jj9987]

22 minutes ago, Eigenvektor said:

The master boot record is a specific sector of the disk that is read by the BIOS/UEFI to determine where to boot from.

 

So it's not a partition as such, nor is it tied to any partition. It's simply a well defined region of the disk where boot records are located.

To add on this - MBR contains the partition table of the disk, which includes

- boot records, meaning where on the disk are the OS boot files (1 or more partitions).

- what other partitions are on the disk

 

Every disk has it's own MBR. You can also have a drive without any boot records, but it still has an MBR to save the partition table information.

An alternative to MBR is GPT - GUID Partition Table.

[Master Disaster]

MBR is not a partition, its technical definition is as boot sector and its a the space contained on the very first sector (sector 0) of a drive, it is hardware reserved meaning it cannot be used for other purposes

 

MBR and bootloader are not the same thing, a bootloader is a piece of code that lives inside the MBR region of the disc along with partition layout data for primary and extended partitions.

 

Traditional MBR uses exactly 512k (which is one sector of a platter) and is divided into 4 sections, the first 446 bytes are where the bootloader lives, there are 4 x 16 byte sections, one for each possible partition and a 2 byte section left for signing the bootloader code. On later drives this changed to 4096k since that's what platter sectors changed too however even on 4096k sector drives the MBR still only uses 512k.