You can create a snapshot-consistent group to simultaneously take snapshots for multiple disks on one or more Elastic Compute Service (ECS) instances. If a business system spans multiple disks, you can create a snapshot-consistent group to ensure a consistent write order and crash consistency of business system data. This topic describes how to create a snapshot-consistent group.
Scenarios
Snapshot-consistent groups are suitable for the following scenarios:
A business system is deployed in a cluster file system that spans multiple ECS instances and requires point-in-time consistency and crash consistency across databases or enterprise-level applications. For example, a MySQL cluster is built on ECS instances, a logical volume in Logical Volume Manager (LVM) spans multiple volumes, or Oracle or SAP HANA clusters are migrated to the cloud.
Snapshots need to be created simultaneously for multiple nodes of a distributed application system, such as a large-scale website or a multi-application collaborative system.
Disks on multiple ECS instances that reside in the same region need to be backed up at the same time, and high point-in-time consistency is required.
Precautions
Before you use the snapshot-consistent group feature, take note of the following information:
When you create a snapshot-consistent group based on an ECS instance, take note of the following items:
To ensure that services are not affected, we recommend that you create the snapshot-consistent group during off-peak hours.
The ECS instance must be in the Running or Stopped state. Do not perform operations that change the instance status, such as stopping or restarting the instance. Otherwise, snapshots may fail to be created.
You can use the snapshot-consistent group feature to create snapshots only for enhanced SSDs (ESSDs) that are in the In Use state.
If ESSDs and disks of other categories are attached to the ECS instance, you can select only the ESSDs on the instance to create a snapshot-consistent group.
ESSDs that support the multi-attach feature do not support the snapshot-consistent group feature.
A single snapshot-consistent group can contain snapshots of up to 16 disks, including system disks and data disks, and cannot exceed 32 TiB in size.
The snapshots that you create are retained until you delete them. To reduce costs, we recommend that you delete unnecessary snapshots on a regular basis. For information about how to delete a snapshot, see Delete a snapshot.
For the amount of time that is required to create a snapshot-consistent group, take note of the following items:
The amount of time that is required to create a snapshot-consistent group varies based on the sizes of the disks for which you want to create snapshots. The first snapshot of a disk is a full snapshot and takes an extended period of time to be created. Subsequent snapshots of the same disk are incremental snapshots and do not take the same amount of time as the first snapshot to be created. The amount of time required to create an incremental snapshot varies based on the amount of data that is changed since the previous snapshot.
Billing
You can use snapshot-consistent groups free of charge. Snapshots that belong to snapshot-consistent groups are billed based on the amount of storage space that is occupied by the snapshots. For more information, see Snapshots.
Scenario 1: Create a snapshot-consistent group based on a single ECS instance
If you want to back up and restore the data of an instance, you can create a snapshot-consistent group based on the instance.
Log on to the ECS console.
In the left-side navigation pane, choose .
In the upper-left corner of the top navigation bar, select a region.
Find the instance based on which you want to create a snapshot-consistent group and choose in the Actions column.
In the Create Snapshot-consistent Group dialog box, configure the parameters that are described in the following table.
Parameter
Description
Select cloud disk
Select the ESSDs for which you want to create snapshots.
Snapshot parameter settings
Snapshot-consistent Group Name
Enter a name for the snapshot-consistent group to facilitate management.
Description
Enter a description for the snapshot-consistent group to facilitate management.
Tag
Add tag key-value pairs to the snapshot-consistent group to facilitate management.
Snapshot speed available
Enable Instant Access: You can select this check box to enable the instant access feature. By default, this check box is not selected.
Snapshot Speed Available Duration: If you select the check box, you can specify a validity period for the instant access feature. The default validity period is one day. The instant access feature is automatically disabled when the specified validity period ends.
NoteFrom 11:00 on October 12, 2023, canary release is performed by region to upgrade the instant access feature, and new snapshots of ESSDs at the performance levels 0, 1, 2, and 3 and ESSD AutoPL disks are instantly available after creation without the need for additional configurations. For more information, see Use the instant access feature.
Application-consistent Snapshot
Enable Application-consistent Snapshot: You can select this check box to enable the application-consistent snapshot feature. By default, this check box is not selected.
You can use application-consistent snapshots for data rollback to prevent logs from being rolled back when applications such as databases start and to ensure that applications start in a consistent state. For more information, see Create application-consistent snapshots in the ECS console.
NoteThe application-consistent snapshot feature is available in the following regions: China (Hong Kong), Singapore, China (Hangzhou), China (Shanghai), and China (Beijing).
Click OK.
After the snapshot-consistent group is created, you can choose
and click the Snapshot-consistent Groups tab to view the snapshot-consistent group.
Scenario 2: Create a snapshot-consistent group based on multiple ECS instances
If you want to back up and restore the data of multiple instances at the same time, you can create a snapshot-consistent group based on the instances.
Log on to the ECS console.
In the left-side navigation pane, choose .
In the upper-left corner of the top navigation bar, select a region.
To create a snapshot-consistent group based on multiple instances, select the region in which the instances reside. For example, to create a snapshot-consistent group based on ECS instances that reside in the China (Hohhot) region, select China (Hohhot) from the drop-down list.
Click the Snapshot-consistent Groups tab. Then, click Create Snapshot-consistent Group.
On the Create Snapshot-consistent Group page, configure the parameters that are described in the following table.
Parameter
Description
Data Source
Select the instances based on which you want to create the snapshot-consistent group. You can search for instances only by instance ID. You can select one or more instances.
Select cloud disk
Select the ESSDs for which you want to create snapshots. Take note of the following items:
You can select only ESSDs.
You can select up to 16 disks, including system disks and data disks. The total size of the selected disks cannot exceed 32 TiB.
Snapshot parameter settings
Snapshot-consistent Group Name
Enter a name for the snapshot-consistent group to facilitate management.
Description
Enter a description for the snapshot-consistent group to facilitate management.
Tag
Add tag key-value pairs to the snapshot-consistent group to facilitate management.
Snapshot speed available
Enable Instant Access: You can select this check box to enable the instant access feature. By default, this check box is not selected.
Snapshot Speed Available Duration: If you select the check box, you can specify a validity period for the instant access feature. The default validity period is one day. The instant access feature is automatically disabled when the specified validity period ends.
NoteFrom 11:00 on October 12, 2023, canary release is performed by region to upgrade the instant access feature, and new snapshots of ESSDs at the performance levels 0, 1, 2, and 3 and ESSD AutoPL disks are instantly available after creation without the need for additional configurations. For more information, see Use the instant access feature.
What to do next
After you create a snapshot-consistent group, you can perform the following operations:
Use the snapshot-consistent group to roll back disks. For more information, see Roll back disks by using a snapshot-consistent group.
Access the snapshot-consistent group and create a custom image from a snapshot that belongs to the group. For more information, see Create a custom image from a snapshot.