# Scenarios and Disk Partitions

If you have added a data disk during ECS creation, you must initialize the data disk after logging in to the ECS.

#### Scenarios

After a disk is attached to a server, you need to log in to the server to initialize the disk, that is, format the disk. You must initialize a disk before accessing it.

- System disk

  A system disk does not require manual initialization because it is automatically created and initialized upon server creation. The default disk partition style is master boot record (MBR).

- Data disk
  - If a data disk is created along with a server, it will be automatically attached to the server.
  - If a data disk is created separately, you need to manually attach it to a server.

  In both cases, you must initialize the data disk before using it. Choose a proper disk partition style based on your service plan.

#### Disk Partition Styles

Table 1 lists the common disk partition styles. In Linux, different disk partition styles require different partitioning tools.

Table 1 Disk partition styles
Disk Partition Style | Maximum Disk Capacity Supported | Maximum Number of Partitions Supported | Linux Partitioning Tool
--- | --- | --- | ---

Master Boot Record (MBR)

2 TB

- 4 primary partitions
- 3 primary partitions and 1 extended partition

With MBR, one may create several primary partitions and an extended partition. An extended partition must be divided into several logical partitions before use. For example, if 6 partitions need to be created, you can create the partitions in the following two ways:

- 3 primary partitions and 1 extended partition, with the extended partition divided into 3 logical partitions
- 1 primary partition and 1 extended partition, with the extended partition divided into 5 logical partitions

- fdisk
- parted

GUID Partition Table (GPT) | 18 EB 1 EB = 1048576 TB | Unlimited Disk partitions created using GPT are not categorized. | parted

The maximum disk capacity supported by MBR is 2 TB, and that supported by GPT is 18 EB. Because a data disk currently supports up to 32 TB, use the GPT partition style if your disk capacity is larger than 2 TB.

If you change the disk partition style after the disk has been used, the data on the disk will be cleared. Therefore, select a proper disk partition style when initializing the disk.

Parent topic: Initializing EVS Data Disks