Overview of snapshot-consistent groups - Elastic Compute Service

A snapshot-consistent group is an advanced data protection feature that enables you to simultaneously create snapshots for multiple cloud disks across one or more ECS instances within the same zone. This ensures all snapshots capture data at the exact same point in time, providing both crash consistency and point-in-time consistency.

Scenarios

Snapshot-consistent groups are commonly used in the following scenarios:

Cluster file systems and database applications
This applies to databases or enterprise applications deployed across ECS instances in a cluster file system where both point-in-time consistency and crash consistency are required. For example, a self-managed MySQL cluster with databases distributed across multiple ECS instances—each instance using several disks for data storage—benefits from snapshot-consistent groups. When backing up the entire cluster, all disks are synchronized, avoiding recovery failures or data corruption caused by asynchronous data.
Distributed application systems
For large websites or multi-application collaborative systems, data may be stored across different ECS instances but remain tightly linked by logic. Snapshot-consistent groups allow these systems to quickly capture consistent snapshots of all related disks before upgrades, migrations, or failbacks, ensuring uniform system states and full traceability.
Batch backup requirements
When you need periodic backups of multiple ECS instances in the same zone—especially for time-sensitive applications—snapshot-consistent groups provide an efficient way to perform backups while maintaining data consistency. This simplifies management and reduces risk.

Features

The following table describes common features of snapshot-consistent groups, from creation to deletion.

Feature	Description
Create a snapshot-consistent group	You can create a snapshot-consistent group to simultaneously create snapshots for multiple cloud disks on one or more ECS instances in the same zone.
Create application-consistent snapshots	If you require stricter data consistency, enable the application-consistent snapshot feature when creating a snapshot-consistent group. The system creates either application-consistent snapshots or file system-consistent snapshots based on actual conditions.
Roll back disks using a snapshot-consistent group	If your system fails due to hardware or software issues—or if data loss or exceptions occur from accidental operations—you can roll back one or more cloud disks using a snapshot-consistent group. This restores disk data to its state before the accidental operation, ensuring data durability and business continuity.
Modify and delete a snapshot-consistent group	You can change the name and description of a snapshot-consistent group. If you no longer need the group, delete it along with its snapshots to avoid ongoing snapshot storage fees. Important Deleting a snapshot-consistent group deletes all snapshots in the group. Deleted snapshots cannot be restored, and their data cannot be recovered. Confirm that you no longer need the snapshots before deleting the group.

Billing

You can create a snapshot-consistent group at no cost. However, you are charged snapshot storage fees based on the size and duration of snapshots created using the group. For more information, see Snapshot billing.

Limits

When you use snapshot-consistent groups, note the following limits:

Limit	Description
Block Storage Class	Only Enterprise SSD (ESSD) series disks (ESSDs, ESSD AutoPL disks, ESSD Entry disks, and ESSD Zonal Redundant disks) support snapshot-consistent groups—and only if the multi-attach feature is disabled. Important ESSD Zonal Redundant disks can only be grouped with other ESSD Zonal Redundant disks. Only ESSDs support application-consistent snapshots. Local disks and elastic ephemeral disks do not support snapshot-consistent groups or application-consistent snapshots.
Other limits	The cloud disks you want to include in a snapshot-consistent group must be in the same zone. Snapshots created using a snapshot-consistent group do not support custom retention periods. By default, snapshots are retained until you manually delete them. You can create a snapshot-consistent group across multiple ECS instances. Each group can contain snapshots of up to 16 cloud disks—including system and data disks—with a total capacity limit of 32 TiB. You cannot create application-consistent snapshots across instances in the ECS console. Total concurrent quota: A single cloud disk can have up to 10 active snapshot tasks—including manual snapshots, automatic snapshots, and snapshot-consistent group tasks. Concurrent snapshot-consistent group tasks have the following limits: China (Hohhot), Philippines (Manila), China (Ulanqab), China (Heyuan), China (Guangzhou), Indonesia (Jakarta), Thailand (Bangkok), China (Hong Kong), China (Qingdao), China (Zhangjiakou), China (Beijing), China (Shenzhen), China (Hangzhou), and China (Shanghai): No per-task limit. You can create multiple concurrent snapshot-consistent groups, subject only to the overall 10-task concurrency limit. After reaching the limit, you cannot select disks for new snapshot-consistent group tasks. All other regions: A single cloud disk supports only 1 active snapshot-consistent group task. If one is already running—even if fewer than 10 total snapshot tasks are active—you cannot select that disk for another snapshot-consistent group task.