The Alibaba Cloud snapshot service is an agentless data backup service that allows you to create crash-consistent snapshots for system disks or data disks. You can use snapshots to back up data, restore Elastic Compute Service (ECS) instances that were released by mistake, and create custom images. Before you roll back disks, modify critical system files, or change the operating system of an instance, you can create snapshots for disks to improve fault tolerance.
Prerequisites
ECS Snapshot is activated. For more information, see Activate ECS Snapshot.
The disk for which you want to create a snapshot is in the In Use or Unattached state. Take note of the following items:
If the disk is in the In Use state, make sure that the ECS instance to which the disk is attached is in the Running or Stopped state.
If the disk is in the Unattached state, make sure that the disk was attached to an ECS instance at least once. Snapshots cannot be created for cloud disks that have never been attached to an ECS instance.
Precautions
It can take several minutes to create a snapshot. The amount of time required to create a snapshot for a disk varies based on the amount of data that is written to the disk. The first snapshot of each disk is a full snapshot and takes an extended period of time to be created. Subsequent snapshots of the disk are incremental snapshots and do not take as long to be created as the full snapshot. The amount of time required varies based on the amount of data that is modified from the previous snapshot. As the amount of modified data increases, the amount of time required to create an incremental snapshot increases.
When you create a snapshot, take note of the following items:
Do not perform operations that change the status of the instance, such as stopping or restarting the instance.
You are charged for snapshots. For more information, see Snapshots.
We recommend that you create snapshots during off-peak hours because snapshot creation degrades the I/O performance of disks by up to 10% and slows down data reads and writes.
If operations are performed on the disk and incremental data is generated when a snapshot is being created, the incremental data is not included in the snapshot.
If you create an extended volume from a single multi-partition disk, the snapshot that you created can be used to roll back the disk.
When a disk is used to create a dynamic extended volume or a RAID array, we recommend that you create a snapshot-consistent group and enable the application-consistent snapshot feature. For more information, see Create a snapshot-consistent group and Create application-consistent snapshots in the ECS console.
Snapshots that you created are stored indefinitely until you delete the snapshots. We recommend that you delete the snapshots that you no longer require on a regular basis to prevent excess snapshot storage fees.
This topic describes how to create a snapshot for a single disk. If you want to simultaneously create snapshots for multiple disks on one or more instances, use the snapshot-consistent group feature. For more information, see Create a snapshot-consistent group. When 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.
Procedure
You can go to the Snapshots page in the ECS console and perform the following operations to create a snapshot for a disk:
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.
On the Disk Snapshots tab, click Create Disk Snapshot.
In the Create Disk Snapshot dialog box, configure the parameters that are described in the following table.
Parameter
Description
Disk
The disk for which you want to create a snapshot.
Snapshot Name
The name of the snapshot.
Snapshot Type
The type of the snapshot. Select Normal Snapshot or IA Snapshot.
Normal Snapshot: It can take several minutes to create a snapshot. The amount of time required to create a snapshot for a disk varies based on the size of the snapshot. The first time you create a snapshot for the selected disk, the process requires a long period of time to complete.
IA Snapshot: You can create IA snapshots only for enhanced SSDs (ESSDs) at the performance levels 0, 1, 2, and 3 (PL0, PL1, PL2, and PL3 ESSDs) and ESSD AutoPL disks. For more information, see Use the instant access feature.
After snapshots are created, you are charged the snapshot storage fees per region based on the total size of the snapshots that are stored in the region. For information about more billing rules of snapshots, see Snapshots.
Retention Period
The number of days during which the snapshot is retained. You can select Permanently or Retained For. After the retention period of the snapshot ends, the system automatically deletes the snapshot.
NoteIf the snapshot is three days away from being released, Released After {days} Days is displayed in the Retention Period column corresponding to the snapshot.
If you set Retention Period to Retained For and the snapshot is created, find the snapshot in the snapshot list and click the
icon in the Retention Period column to extend the retention period. Alternatively, you can find the snapshot and choose 
> Extend Retention Period in the Actions column to extend the retention period.
Tag
The tag that you want to add to the snapshot. You can use tags to classify snapshots for easy search and batch operations.
Resource Group
The resource group to which to assign the snapshot. You can use resource groups to manage snapshots at different levels.
Click OK.
After you create the snapshot, you can view the snapshot on the Disk Snapshots tab.
You can also create a snapshot for a disk on the Disks page in the ECS console. To go to the Disks page, choose in the left-side navigation pane.
What to do next
After you create a snapshot, you can use the snapshot to perform the following operations: