Snapshots are essential for disaster recovery, providing complete point-in-time replicas of cloud disk data. They enable periodic backups of business data on cloud disks, protecting against data loss from accidental operations, attacks, or viruses. In the event of data loss or anomalies on a cloud disk, snapshots facilitate the restoration of disk data to a previous state, ensuring uninterrupted business operations.
Important
Elastic Compute Service (ECS) instances do not automatically back up data on cloud disks. To safeguard against data loss from major O&M operations, such as configuration changes and upgrades, attacks, or viruses, we recommend establishing periodic snapshot policies to back up cloud disk data following the creation of ECS instances.
Scenarios
Snapshots are recommended for use in the following scenarios:
Daily data backup
Automatic snapshot policies can be configured to create snapshots of cloud disks at regular intervals, retaining them for a specified duration to protect against data loss due to accidental operations, attacks, or viruses.
Disaster recovery and fault tolerance
Prior to O&M activities such as capacity expansion, configuration changes, and migration on ECS instances and cloud disks, manual snapshots can be created for data backup, allowing for data restoration from snapshots when necessary.
Fast data restoration
In the event of software compatibility issues during an upgrade or service interruptions for other reasons, snapshots can be used to roll back cloud disks, swiftly restoring business data and maintaining business continuity.
Batch business deployment
Custom images created from snapshots enable the efficient batch deployment or upgrade of business across multiple sites by creating ECS instances.
Batch data distribution
For rapid distribution of business data, cloud disks can be batch created from snapshots and attached to ECS instances according to business needs.
Note
Snapshots serve as a means to back up or clone individual disks or disk groups. To back up or clone an entire ECS instance, including all its disks, you can utilize the ECS full backup functionality provided by Cloud Backup.
Get started with snapshots
Snapshot principles
Alibaba Cloud snapshots offer full or incremental backups of data on cloud disks. The initial snapshot of a cloud disk is a full snapshot, capturing all data at the time of creation. Subsequent snapshots are incremental, recording only new or altered data since the last snapshot, thus optimizing storage space and reducing costs.
Both full and incremental snapshots contain information about all data blocks on the cloud disk, enabling restoration to the exact state at the snapshot's creation time. Deleting a snapshot still allows for restoration using any remaining snapshots to their respective points in time. For more information, see the referenced document.
Snapshot storage location
Snapshots are securely and automatically stored in Alibaba Cloud Object Storage Service (OSS) for long-term retention and flexible restoration. For security reasons, you cannot use your own OSS buckets for snapshot storage.
By default, snapshots are stored in zone-redundant storage (ZRS) buckets in regions where OSS supports ZRS, enhancing data redundancy.
In regions where OSS does not support zone-redundant storage (ZRS), snapshot data is stored in locally redundant storage (LRS) buckets. For businesses requiring high availability, it is recommended to use snapshot replication to enhance data backup across regions.
To learn about the regions where OSS offers zone-redundant storage, please refer to data redundancy and how to create a zone-redundant storage bucket.
Note
After using a snapshot to create or roll back a disk, the snapshot's data blocks begin loading from OSS to the disk. Accessing data not yet loaded prompts immediate loading from OSS. The loading duration varies with snapshot size, increasing read latency until all data is loaded and normal latency resumes.
Instant access snapshots
Creating a snapshot for a disk with a large amount of data takes more time, as does uploading the snapshot to Object Storage Service (OSS). The instant access (IA) feature enables you to utilize snapshots within seconds after they are created, rather than waiting for the upload to OSS to complete. IA snapshots can be used for a variety of tasks, including creating cloud disks, reverting cloud disks to a previous state, and sharing snapshots with others. For more information, see instant access snapshots.
Snapshot data security
To fulfill security and compliance requirements, we recommend encrypting snapshots during storage and backup. Encrypted snapshots ensure the confidentiality and integrity of data backups, including system and data disks, even in the event of data breaches.
Snapshots inherit the encryption attribute of the cloud disk they are created from, maintaining encryption during storage, transmission, and even when copied to another region or used for disk restoration. For more information, see data confidentiality.
Snapshot functionality
The following figure illustrates the common features provided by snapshots.
Feature | Description | References |
Feature | Description | References |
Create snapshots | Snapshots can be created manually or automatically: | |
Copy snapshots | Copy snapshots between regions to achieve cross-regional data backup. | Snapshot Duplication |
Share snapshots | Share snapshots with other Alibaba Cloud accounts or within your organization to enable quick disk creation for daily O&M needs. | Snapshot Sharing |
Roll back disks using snapshots | Use snapshots to revert cloud disks to a previous state in case of system faults or accidental data loss. | |
Creating a Disk from a Snapshot | You can create a new cloud disk from a snapshot, which will contain data identical to that of the original cloud disk at the time the snapshot was taken. This feature enables the replication of cloud disk data within or across zones. | Creating a Data Disk from a Snapshot |
Creating a Custom Image from a System Disk Snapshot | You can create a custom image using a system disk snapshot to replicate the operating system and data of an ECS instance. This custom image can then be used to quickly launch multiple ECS instances, streamlining the replication of application environments. | Create a Custom Image from a Snapshot |
Billing description
Before you can create snapshots, you must activate the Snapshot service. You are not charged for activating the Snapshot service, but you are charged for the snapshots that you create. By default, manual snapshots and automatic snapshots are standard snapshots. You are charged storage fees for standard snapshots based on the size and storage duration (billable duration) of the snapshots in each region.
If you use the snapshot replication feature to copy a snapshot from one region to another region, you are charged a data transfer fee for the snapshot replication and a storage fee for the new standard snapshot (snapshot copy) in the destination region.
For more details on snapshot billing, see snapshot billing.
Limits
Limit item | Description |
Snapshot quota | The number of snapshots that can be retained for each cloud disk: The number of automatic snapshot policies that can be retained for each account in a single region: 100 The number of automatic snapshot policies that can be associated with each cloud disk: 1 The number of concurrent snapshots that can be created for each cloud disk: 1
|
Supported cloud disk types | Manual and automatic snapshots can be created for all types of cloud disks . Only ESSD series cloud disks (ESSD, ESSD AutoPL, and ESSD Entry) support the snapshot-consistent group feature, and the cloud disks do not have the multi-attach feature enabled.
|
Local disks and elastic ephemeral disks | Manual snapshots, automatic snapshots, and snapshot-consistent groups are not supported. |
Instant access snapshots | Only ESSD series cloud disks (ESSD, ESSD AutoPL, ESSD Entry, and ESSD ZRS) support the instant access feature. |
Download or export snapshots | Not supported. You can first create a custom image from a snapshot and then export the custom image to your local device. |
FAQ
For answers to frequently asked questions about snapshot usage, please refer to the snapshot FAQ.