All Products
Search
Document Center

Elastic Compute Service:Snapshot-consistent groups

Last Updated:Apr 01, 2025

A snapshot-consistent group is an advanced data protection feature that allows you to simultaneously create snapshots for multiple cloud disks on one or more Elastic Compute Service (ECS) instances in the same zone. This feature ensures that snapshots accurately back up the data's state at a specific point in time, providing both crash consistency and point-in-time consistency.

Scenarios

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

  • Cluster file systems and database applications

    In cluster file systems and database applications that spread across ECS instances, point-in-time consistency and crash consistency are essential. For example, a MySQL cluster with databases distributed over multiple ECS instances, each with several disks, benefits from snapshot-consistent groups by synchronizing data across all disks during backup, preventing recovery failures or data corruption due to asynchronous data.

  • Distributed application systems

    Snapshot-consistent groups aid large websites or multi-application collaborative systems in obtaining consistent snapshots of all associated disks before upgrades, migrations, or failbacks, ensuring uniform system states and traceability.

  • Batch backup requirements

    For periodic backups of multiple ECS instances in the same zone, especially for time-sensitive applications, snapshot-consistent groups offer an efficient solution to execute backups while maintaining data consistency, streamlining management, and mitigating risks.

Features

The following figure shows the common features of snapshot-consistent groups from creation to deletion.

image

The following table describes the common features of snapshot-consistent groups.

Feature

Description

Create a snapshot-consistent group

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 data consistency, enable the application-consistent snapshot feature when you create a snapshot-consistent group. The system creates application-consistent snapshots or file system-consistent snapshots based on the actual situation.

Roll back disks by using a snapshot-consistent group

If system faults occur, such as hardware or software issues, or if data loss or exceptions occur due to accidental operations, you can roll back one or more cloud disks by using a snapshot-consistent group. This restores the disk data to the state before the accidental operations were performed and ensures data durability and business continuity.

Modify and delete a snapshot-consistent group

You can change the name and modify the description of a snapshot-consistent group. If you no longer require a snapshot-consistent group, you can delete the group and the snapshots in it to prevent unnecessary costs.

Important

When you delete a snapshot-consistent group, the snapshots in it are also deleted. Deleted snapshots cannot be restored, and the snapshot data cannot be recovered. Make sure that you no longer require the snapshots in a snapshot-consistent group before deleting it.

Billing

You can create a snapshot-consistent group free of charge, but you are charged snapshot storage fees based on the size and usage duration of the snapshots created by using the group. For more information, see Snapshots.

Limits

When you use snapshot-consistent groups, take note of the limits described in the following table.

Limit

Description

Disk category

  • Only Enterprise SSD (ESSD) series disks (ESSDs, ESSD AutoPL disks, and ESSD Entry disks) with multi-attach disabled support snapshot-consistent groups.

  • 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 for which you want to create a snapshot-consistent group must be in the same zone.

  • Snapshots created by using a snapshot-consistent group do not support custom retention periods. By default, the snapshots are retained until you manually delete them.

  • You can create a snapshot-consistent group for multiple ECS instances. Each snapshot-consistent group can contain snapshots of up to 16 cloud disks, including system disks and data disks, and the total capacity cannot exceed 32 TiB in size.

  • You cannot create application-consistent snapshots across instances in the ECS console.