Attach cloud disks to ECS instances as system disks or data disks to provide persistent block storage.
System disk
A system disk stores operating system data and is created together with the instance. Each instance has one unique system disk that cannot be shared with other instances. See Create and use a system disk.
Data disk
A data disk stores application data. You can create a data disk with an instance or attach one later. The maximum number of data disks per instance varies by instance type. See Instance families available for purchase and Create and use a data disk.
Common operations
|
Lifecycle |
System disk |
Data disk |
|
|
Creation phase |
Create a cloud disk separately. |
Not supported. Note
The system disk is created with the instance and automatically attached and initialized. |
Supported. |
|
Attach a cloud disk. |
Not required. The system disk is automatically attached during instance creation. |
Required. |
|
|
Initialize a cloud disk. |
Not required. The system disk is automatically initialized during instance creation. |
Required. |
|
|
O&M phase |
Replace the operating system. |
Supported. |
Not supported. Note
Only system disks contain the boot images. Data disks do not support OS replacement. |
|
Others |
Supported. |
Supported. |
|
|
Release phase |
Release a cloud disk separately. |
Not supported. Note
The system disk is released with its instance. If you disable the Release Disk with Instance feature, the system disk is retained as a data disk after the instance is released. |
Supported. |
References
See Overview of Block Storage for disk categories.
Call DescribeInstanceTypes to query the maximum number of cloud disks per instance type.