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

System disk
When a server is created, a system disk is automatically initialized with Master Boot Record (MBR).
Newly created empty data disk
After you attach a newly created empty data disk to a server, you must initialize the disk including creating partitions, creating file systems, and mounting the partitions before you can use the disk.
- If a data disk is created together with a server, EVS automatically attaches it to the server. You only need to initialize it to make it available for use.
- If a data disk is created explicitly, you need to first attach it to a server and then initialize it.
For details, see Table 1.
Existing data disk
An existing data disk is a disk created from a snapshot, a backup, or an image, or a disk detached from one server and then attached to another.
- You can choose not to re-partition the disk, but use the existing disk partitions.
  - In Linux, create new mount points and mount the partitions, and configure auto mount at system startup.
  - In Windows, no further action is required. You can simply use the existing partitions.
- You can also re-initialize the data disk.
  Re-partitioning a disk will erase all the existing data on the disk, so you are advised to use snapshots to back up the disk data first.
  - In Linux, unmount the partitions, delete them (by running fdisk data-disk-name, entering d and the partition number, and entering w), and then re-initialize the disk.
  - In Windows, delete the partitions (using the volume deletion tool) and then re-initialize the disk.
  For details, see Table 1.

Impact on the System

An initialization operation includes partitioning, which deletes all the data on the disk.
If you change the partition style of a disk, data on the disk will be erased. Select an appropriate partition style when initializing disks.
Initializing a disk does not delete the snapshots created for the disk, so you can still use snapshots to roll back data to the source disk after the disk is initialized.

Procedure

Major initialization steps include creating partitions and file systems, mounting partitions, and configuring auto mount at system startup. In Linux, you can choose different partition styles based on your disk capacity. For details, see Table 2.

The maximum disk size that MBR supports is 2 TiB, and that GPT supports is 18 EiB. If your disk is greater than 2 TiB or you plan to expand it to over 2 TiB later, use GPT when initializing disks.

**Table 1** Disk initialization instructions
Disk Capacity	Partition Style	Operating System	Reference
Capacity ≤ 2 TiB	Guid Partition Table (GPT) or Master Boot Record (MBR)	Linux	Initializing a Linux Data Disk (Less Than or Equal to 2 TiB)
Capacity ≤ 2 TiB	Guid Partition Table (GPT) or Master Boot Record (MBR)	Windows	Initializing a Windows Data Disk
Capacity > 2 TiB	GPT	Linux	Initializing a Linux Data Disk (Greater Than 2 TiB)
Capacity > 2 TiB	GPT	Windows	Initializing a Windows Data Disk

Partition Styles

Common disk partition styles include MBR and GPT. In Linux, you can choose different partition styles based on your disk capacity, as described in Table 2.

**Table 2** Disk partition styles
Partition Style	Max. Disk Capacity Supported	Max. Number of Partitions Supported	Linux Partitioning Tool	Reference
MBR	2 TiB	MBR partitions include primary partitions and extended partitions. A maximum of four primary partitions are supported. If you need more partitions, create one extended partition. Example: Four primary partitions Three primary partitions and one extended partition The extended partition must be divided into logical partitions before use. For example, you can create six partitions in the following two ways: Three primary partitions and one extended partition, with the extended partition divided into three logical partitions One primary partition and one extended partition, with the extended partition divided into five logical partitions	fdisk parted	Initializing a Linux Data Disk (Less Than or Equal to 2 TiB) Initializing a Windows Data Disk
GPT	18 EiB 1 EiB = 1,048,576 TiB	Not limited GPT partitions are not categorized.	parted	Initializing a Linux Data Disk (Greater Than 2 TiB) Initializing a Windows Data Disk

Disk Partition Styles

Table 3 lists the common disk partition styles. In Linux, different partition styles require different partitioning tools.

**Table 3** Disk partition styles
Disk Partition Style	Maximum Disk Capacity Supported	Maximum Number of Partitions Supported	Linux Partitioning Tool
Master Boot Record (MBR)	2 TiB	4 primary partitions 3 primary partitions and 1 extended partition With MBR, you can create several primary partitions and one extended partition. The extended partition must be divided into logical partitions before use. For example, if 6 partitions need to be created, you can create them 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 EiB 1 EiB = 1048576 TiB	Unlimited Disk partitions created using GPT are not categorized.	parted

The maximum disk size supported by MBR is 2 TiB, and that supported by GPT is 18 EiB. Because an EVS data disk currently supports up to 32 TiB, use GPT if your disk size is greater than 2 TiB.

If the partition style is changed after the disk has been used, all data on the disk will be lost, so take care to select an appropriate partition style when initializing the disk. If you must change the partition style to GPT after a disk has been used, it is recommended that you back up the disk data before the change.

Parent topic: Initializing EVS Data Disks

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