A snapshot is a point-in-time backup of disk data. The first snapshot for a disk is a full snapshot that captures all written data blocks (empty blocks are excluded). Subsequent snapshots of the same disk are incremental snapshots that capture only the data blocks changed since the previous snapshot.
ENS snapshots are crash-consistent: only data already written to disk at the moment of creation is captured. Data held in memory or pending I/O operations is not included.
ENS does not automatically create snapshots. All snapshots must be created manually. Create snapshots before high-risk operations such as configuration changes, upgrades, or migrations so you can recover if something goes wrong.
Features
Feature | Description |
Create a snapshot | You can create snapshots in the following ways:
|
Roll back a disk | Restore a disk to a previous state using a snapshot when the system is unresponsive or accidental changes are made. |
Create an image from a system disk snapshot | Create a custom image from a snapshot that contains the OS and data of an ENS instance, then use that image to create multiple instances with identical environments. |
Create a disk from a snapshot | Create multiple identical disks from a single snapshot. |
Replicate a snapshot across nodes | Copy a snapshot from one node to another to create a replica in the destination node. |
Limitations
Snapshots can only be created for ultra disks or all-flash disks.
Images cannot be created from data disk snapshots.
Snapshots can only be replicated to nodes that support ultra disks or all-flash disks.
A single account can retain a maximum of 100 snapshot policies.
Each cloud disk can be associated with a maximum of 1 automatic snapshot policy.
Each cloud disk can retain a maximum of 100 automatic snapshots.
Billing
Snapshot storage is billed on a pay-as-you-go basis by month. You are charged based on the actual storage space the snapshot occupies — not the provisioned disk size.
Storage usage
Formula: Storage fee = Unit price × Storage usage (GB) × Billing duration (months)
Disk type | Unit price |
Ultra disk | USD 0.0493 per GB-month |
All-flash disk | USD 0.1408 per GB-month |
Billing duration: Starts when the snapshot is created and ends when it is deleted. A snapshot that exists for 21 days counts as 21 ÷ 30 = 0.7 months.
Cross-node snapshot replication
When you replicate a snapshot to another node, charges apply to both the replication traffic and the snapshot storage in the destination node.
The first replication of a disk snapshot is a full copy containing all data on the disk.
Subsequent replications of the same disk to the same node are incremental, capturing only data changed since the previous replica.
Formula: Replication traffic fee = USD 0.05 per GB × Storage usage (GB) × 2
The multiplier of 2 accounts for traffic generated in both the source node and the destination node.
Billing examples
Example of snapshot size billing
On the first day of a month, User B creates a total of 100 GB of snapshots for an ultra disk and releases all of them on the 21st day. Also on the first day, User B creates 50 GB of snapshots for an all-flash cloud disk and keeps them for the entire month.
Therefore, the snapshot capacity fee for the month is CNY 0.35/GB/month × 100 GB × (21/30) + CNY 1/GB/month × 50 GB × 1 month = CNY 74.5.
Example of cross-edge-zone snapshot replication traffic billing
On a given day in a calendar month, User B copies a 100 GB snapshot from an edge zone in Hangzhou to an edge zone in Beijing. This operation creates a 100 GB snapshot replica in the Beijing edge zone.
The cross-edge-zone snapshot replication traffic fee is calculated as follows: USD 0.05/GB × 100 GB × 2 = USD 10.
Use cases
Daily data backup: Use an auto snapshot policy to periodically create snapshots for your cloud disks and retain them for a specified duration. This provides routine data backup to protect against data loss caused by accidental operations, virus infections, or malicious attacks.
Protection for high-risk operations: Before performing scaling, specification changes, or migrations on your ENS instances and cloud disks, create a manual snapshot in advance. If issues arise during the operation, you can quickly recover your business from the snapshot.
Quick data recovery: If your system experiences service interruptions due to software compatibility issues or other causes during upgrades, you can roll back the cloud disk from a historical snapshot to quickly restore business continuity. For details, see Create and manage snapshots.
Batch deployment across sites: Create a custom image from a snapshot to efficiently deploy or upgrade multiple sites with identical environments in bulk.
Batch data distribution: Create new cloud disks in bulk from snapshots and attach them to ENS instances as needed for rapid data distribution across your infrastructure.
What's next
Create a snapshot
Roll back a disk using a snapshot
Replicate a snapshot across nodes