Alibaba Cloud's cloud disks provide persistent storage solutions for Elastic Compute Service (ECS) instances. They can be mounted as either system disks or data disks on ECS instances, playing a crucial role in the operation of ECS instances.
System disk
The system disk stores operating system data and is created alongside the instance. It houses the image necessary to boot the instance. Each instance is allocated a distinct system disk, which cannot be interchanged with the system disk of another instance. For instructions on managing system disks, see the guide to creating and using system disks.
Data disk
The data disk is designated for storing application-related data. It can be created during the instance setup or while the instance is active. The maximum number of disks that can be mounted varies by instance type. For details, see Instance Family. For instructions on managing data disks, see the guide to creating and using data disks.
Comparison of common operations for system disks and data disks
Lifecycle | System disk | Data disk | |
Creation phase | Create disk separately | Not supported Note The system disk can only be created with the instance. After creation, mounting and initialization are automatically completed without additional operations. | Supported |
Mount disk | Not applicable | Requires execution | |
Initialize disk | Not applicable | Requires execution | |
O&M phase | Change operating system | Supported | Not supported Note The system disk contains the image used to boot the instance, so the data disk does not involve changing the operating system. Additionally, operations during the O&M phase are similar. |
Other operations | Supported | Supported | |
Release phase | Release disk separately | Not supported Note The system disk can only be released with the instance and cannot be released separately. Both system disks and data disks can be set to not release with the instance. The difference is that after the instance is released, the system disk will be retained as a data disk, losing its system disk properties. | Supported |
Related operations
To learn more about the types of disks available, see Overview of Block Storage.
You can also retrieve the maximum number of disks supported by different instance types using the DescribeInstanceTypes API.