A snapshot is a copy of data on a cloud disk or Shared Block Storage (hereinafter referred to as disks) at a specified time point. A snapshot is commonly used for data backup, disk recovery, replacing the operating system on an instance, and creating custom images.

Note Creation of a snapshot may temporarily reduce the I/O performance of a block storage device (generally by no more than 10%), resulting in an instantaneous decrease in the I/O speed. In this case, we recommend that you create snapshots during off-peak hours.

Scenarios

We recommend that you create snapshots for the following scenarios:

  • Create a snapshot for a disk, whose data serves as the base data for another disk.

  • You want to roll back the disk with the snapshot when the data is corrupted. Cloud disks, including Basic Cloud Disks, Ultra Cloud Disks, and SSD Cloud Disks, are a secure means of storage that protects your data assets against loss. If incorrect data is accidentally stored on a disk, application errors lead to data errors, or hackers exploit vulnerabilities in your system and gain access to your data, you can use a snapshot to restore the target disk to a desired state.

  • If you want to purchase an instance that has the same environment as an existing instance, you can create a custom image from the system disk snapshot of the existing instance, and then create an instance with the custom image.

  • Regularly back up critical business data on the system disk and data disk with snapshots, mitigating data loss resulting from misoperations, attacks, and viruses.

  • Before any important operations (such as replacing operating systems, upgrading application software, or migrating business data), we recommend that you create one or more snapshots. In the case of any problems during the upgrade or migration, you can use snapshots to restore the normal system data state in a timely manner.

  • By creating snapshots for the production data, you can provide nearly real-time production data for such applications as data mining, report query, as well as development and testing.

Features

Currently, Alibaba Cloud provides the Snapshot 2.0 service. Compared with the typical snapshot service, Snapshot 2.0 performs better in terms of capacity, scalability, cost-effectiveness, and usability. For more information, see ECS Snapshot 2.0 vs. traditional storage products. Unless otherwise specified, snapshots in all ECS topics refer to the Snapshot 2.0 service.

Classification

Snapshots are classified into two categories:

  • Manual snapshots, which are created manually. You can create snapshots for a disk at any time.

  • Auto snapshots, which are created automatically according to the automatic snapshot policy. You can create an automatic snapshot policy and apply it to the storage device. The snapshots will then be created automatically at the specified time points.

Billing details

Currently, the snapshot service is available free of charge.

Encryption

In scenarios where disk encryption is required, you can set up ECS disk encryption. After that, all snapshots of the disks are encrypted as well. However, any existing snapshots that are not encrypted cannot be converted to encrypted snapshots, the converse scenario is also prohibited. For more information, see ECS disk encryption.

View the size of snapshots

You can view the total size of the snapshots of the disk by using the Snapshot Chains feature in the ECS console.

You can also view the total snapshot size in a region by using the Snapshot Size feature in the ECS console.

Delete snapshots

If you no longer need a snapshot, you can delete the snapshot to guarantee a sufficient snapshot quota. If you have applied an automatic snapshot policy to the disk, you need to delete the automatic snapshot policy.