Initialize a new data disk - Elastic Compute Service - Alibaba Cloud Documentation Center

After you attach a new empty data disk to an Elastic Compute Service (ECS) instance, you must create partitions on the disk and mount file systems to the disk before you can use the disk to store data. This topic describes the scenarios in which cloud disks need to be initialized and how to initialize a cloud disk. This topic also describes the partition formats and device names of cloud disks.

Scenarios

You can initialize only the following new data disks that do not contain data:

Data disks that are created together with ECS instances that run Linux operating systems
Empty data disks that are separately created

Note

You do not need to initialize the system disks that are created together with ECS instances or the data disks that are created together with ECS instances that run Windows operating systems. The disks are automatically partitioned and file systems are automatically mounted to the disks.
In most cases, a disk created from a snapshot contains data. In this case, you need to only mount file systems on the disk or bring the disk online. For more information, see Step 8 in the "Create a data disk from a snapshot" topic.
You do not need to initialize a disk when you test block storage performance or if applications, such as databases, directly perform operations on the disk, because no additional file systems are required.

Procedure

Determine whether a disk needs to be partitioned.
- If the disk needs to be partitioned, you must perform complete initialization operations on the disk, including creating partitions and mounting file systems.
- If the disk does not need to be partitioned, you do not need to create partitions on the disk. On a Linux instance, you need to only perform Step 3: Create and mount file systems on the disk.

Different sizes of cloud disks support different partition formats due to the limitations of partition formats. Select an initialization method based on the size of the cloud disk that you want to initialize.

Note

The maximum size of a partition and the maximum number of partitions per disk vary based on the partition format. For more information, see the Partition formats section of this topic.

Initialize a data disk whose size does not exceed 2 TiB

Operating system	Initialization tool	Partition format	Common file system	References
Linux	Partition: Parted or fdisk File system: e2fsprogs	GUID Partition Table (GPT) (recommended) Master Boot Record (MBR)	Extended File System 4 (Ext4) eXtensible File System (XFS)	Initialize a data disk on a Linux instance
Windows	Disk Management	GPT (recommended) MBR	New Technology File System (NTFS)	Initialize a data disk on a Windows instance

Initialize a data disk whose size exceeds 2 TiB

Operating system	Initialization tool	Partition format	Common file system	References
Linux	Partition: Parted File system: e2fsprogs	GPT	Ext4 XFS	Initialize a data disk on a Linux instance
Windows	Disk Management	GPT	NTFS	Initialize a data disk on a Windows instance

Partition formats

Data disks support the MBR and GPT partition formats. The following table describes the differences between the two partition formats.

Partition format

Maximum partition size

Number of partitions

Description

MBR

2 TiB

An MBR disk can have one of the following groups of partitions:

Four primary partitions
Three primary partitions and one extended partition

MBR partitions are classified into primary, extended, and logical partitions.
Before you can use the extended partition, you must divide the partition into logical partitions. You can create an unlimited number of logical partitions in the extended partition.

GPT

18 EiB (1 EiB = 1,048,576 TiB)

Note

An Alibaba Cloud GPT disk can be up to 32 TiB in size.

Linux: unlimited
Windows: 128

All partitions are primary partitions. No extended partitions or logical partitions exist.

Important

An MBR partition can be up to 2 TiB in size. A GPT partition can be up to 18 EiB in size. If the size of your data disk exceeds 2 TiB or if you want to resize your data disk to larger than 2 TiB, you must use the GPT partition format. If you partition the data disk in the MBR format, you cannot extend the disk to a size larger than 2 TiB. If you extend the data disk in the MBR partition format to a size larger than 2 TiB, you may need to repartition and reformat the disk, which causes data loss.

Device names of data disks on Linux instances

By default, data disks that are attached to Linux instances are automatically assigned device names based on the following naming conventions:

I/O optimized instance:
- The device names of data disks that are attached by using the Non-Volatile Memory Express (NVMe) protocol are in the /dev/nvmeXn1 format. Examples: /dev/nvme1n1, /dev/nvme2n1, and /dev/nvme3n1. For information about disks that support the NVMe protocol, see NVMe disks.
- The device names of data disks that are attached by using protocols other than the NVMe protocol are in the /dev/vd[b-z] format. Examples: /dev/vdb, /dev/vdc, and /dev/vdd.
Non-I/O optimized instances: The device names of data disks that are attached to non-I/O optimized Linux instances are in the /dev/xvd[b-z] format. Examples: /dev/xvdb, /dev/xvdc, and /dev/xvdd.