Creating a Snapshot Consistency Group

Scenarios

When you create snapshots individually for multiple disks, they may be generated at different points in time, which can lead to data inconsistency. For example, in database scenarios where data files and log files are stored on different disks, creating separate snapshots for each disk may result in data corruption or loss because the snapshots do not capture data at the same moment in time. Snapshot consistency groups address this issue by allowing you to create snapshots for disks across one or more servers simultaneously, ensuring write-ordering consistency and crash consistency of the disk data.

Snapshot consistency groups are available only in certain regions. You can check the supported regions on the console.

Impacts on Performance

During the snapshot creation, disk I/Os are affected, so you may experience slow reads or writes at certain points. It is recommended that you create snapshots at off-peak hours.

Billing

Creating a snapshot consistency group is free, but the snapshots created will be billed based on their storage used and usage duration. For details, see Billing for EVS Snapshots.

Constraints

• You can use a snapshot consistency group to create snapshots for up to 64 disks at a time.
• A snapshot consistency group can only contain disks that are in the same AZ.
• If a snapshot is being created for a disk, you can only create a snapshot consistency group after the snapshot is created.

Prerequisites

You can only create snapshot consistency groups for disks in the Available or In-use state. Check the disk status in the status column on the disk list page.

Procedure

1. Sign in to the EVS console.
2. In the navigation pane on the left, choose Elastic Volume Service > Snapshots.

   The Snapshots page is displayed.

3. On the Snapshot Consistency Groups tab, click Create Snapshot Consistency Group in the upper right corner.
4. Configure the required parameters.

   Table 1 Parameter description

   Parameter	Description
   Region	The region to which the snapshot consistency group belongs.
   AZ	The AZ to which the snapshot consistency group belongs.
   Select Servers	Select one or more servers for which you want to create a snapshot consistency group.
   Select Disks	Select one or more disks for which you want to create a snapshot consistency group.
   Group Name	Set a name for the snapshot consistency group.
   Group Description	Optional Set a description for the snapshot consistency group.
   Tag	Optional Tags help you identify and search for cloud resources easier. Add tags if needed.
   Instant Snapshot Restore	Instant Snapshot Restore is supported by default. It allows you to create new disks or roll back disk data, even if snapshots have not yet been uploaded to OBS.
   Enterprise Project	When creating a snapshot consistency group, you can add the group to an existing enterprise project or a new one. An enterprise project enables project-level management and grouping of cloud resources and users. The default project is default.

5. Click Submit.

   After the snapshot consistency group is created, you can view it on the Snapshot Consistency Groups tab.

Helpful Links

• For more snapshot FAQs, see Snapshot.
• To create an individual snapshot, see Creating an EVS Snapshot.
• To roll back disk data from a snapshot consistency group, see Rolling Back Disk Data Using a Snapshot Consistency Group.
• You are advised to delete unnecessary snapshots on a regular basis to reduce snapshot costs. For details, see Deleting a Snapshot Consistency Group.