Basic Information of Extended Partition [MiniTool Wiki]
The so-called extended partition, strictly speaking, is not a real partition. It is just a pointer which is used to point the next partition. Therefore, the master boot sector not only needs primary partition but also should provide a space to store extended partition data. And the extended partition data can help to find the starting position of the second partition. Therefore, no matter how many logical drives are established in the hard disk, the master boot sector can find each of them according to the parameters of the extended partition.
Under Windows, the activated primary partition is the boot partition. It is the first partition on hard disk. And this partition is called C drive in most cases. Under Linux, system can be stored on both primary partition and logical partition. Grub can help to boot computer since it is compatible with Windows.
After dividing primary partition, users can divide the remaining space into an extended partition. Of course, users can divide some remaining space into extended partition. However, some free space would be wasted.
However, the extended partition can't be directly used.
MBR hard disk supports up to 4 primary partitions. If users need more partitions, they need an extended partition record (EBR) which is stored on extended partition. Therefore, users can divide the extended partition into multiple logical drives. But with disk partition software like MiniTool Partition Wizard, you don’t need to create an extended partition before you can create a new logical drive.
Since the master boot record can contain up to 4 entries of primary partition, users can turn to the FDISK partition command to create an extended partition with multiple logical drives. And the information of all logical partitions is stored on the extended partition, while the primary and extended partition information is stored on the MBR of hard disk. In other words, the master boot record only contains the information of primary partition and extended partition regardless of how many partitions are created on the hard disk.