Snapshot Consistency Group overview-Elastic Compute Service(ECS)-阿里云帮助中心

Create snapshots for multiple disks across ECS instances in the same zone with crash consistency and point-in-time consistency.

Use cases

Common use cases for snapshot-consistent groups:

Cluster file systems and database applications

Cluster file systems spanning multiple ECS instances often require point-in-time and crash consistency for databases or enterprise applications. For example, in a self-managed MySQL cluster distributed across multiple ECS instances with multiple disks each, a snapshot-consistent group synchronizes all disks during a full cluster backup, preventing recovery failures or data corruption.
Distributed application systems

In large websites or collaborative systems, data may be distributed across ECS instances with strong logical dependencies. Snapshot-consistent groups capture consistent snapshots of all related disks before an upgrade, migration, or failback, ensuring uniformity and traceability of the system state.
Batch backup requirements

For periodic backup of multiple ECS instances in the same zone, especially time-sensitive applications, snapshot-consistent groups maintain data consistency while simplifying management.

Features

Snapshot-consistent groups support the following operations.

Feature	Description
Create a snapshot consistency group	Simultaneously create snapshots for multiple disks across ECS instances in the same zone.
Create application-consistent snapshots	Enable application-consistent snapshots when creating a snapshot-consistent group for strict data consistency. The system creates application-consistent or file system-consistent snapshots based on your configuration.
Roll back disks using a snapshot-consistent group	Roll back one or more disks to their pre-incident state after a failure, such as a hardware or software issue, or accidental data loss. This ensures data durability and business continuity.
Modify and delete a snapshot-consistent group	Update the name and description of a snapshot-consistent group, or delete a group along with its snapshots to stop incurring charges. Important Deleting a snapshot-consistent group also deletes all snapshots within it. Deleted snapshots cannot be restored. Confirm that you no longer need these snapshots before deletion.

Billing

Creating a snapshot-consistent group is free. However, you incur storage fees for the snapshots in the group, based on snapshot size and retention period. See Snapshot billing.

Limitations

Snapshot-consistent groups have the following limitations:

Limit	Description
Disk type	Only ESSD series disks (ESSDs, ESSD AutoPL disks, ESSD Entry disks, and ESSD zone-redundant disks) support snapshot-consistent groups. Multi-attach must be disabled for the disks. Important ESSD zone-redundant disks can only be grouped with other ESSD zone-redundant disks. Only ESSDs support application-consistent snapshots. Local disks and elastic ephemeral disks support neither snapshot-consistent groups nor application-consistent snapshots.
Other limits	All disks in a snapshot-consistent group must be in the same zone. Snapshots in a snapshot-consistent group do not support custom retention periods and are permanently retained by default. A snapshot-consistent group supports disks across multiple instances. A single group can contain up to 128 disks with a total capacity of up to 256 TiB. The ECS console does not support creating application-consistent snapshots for disks across multiple instances. Concurrent quota: Up to 10 snapshot tasks (Manual Snapshots, Automatic Snapshots, and Snapshot Consistency Group tasks) can run concurrently per disk. When this quota is reached, the disk cannot be added to a new snapshot-consistent group.