Local snapshots provide complete copies of disk data at specific points in time and are an important method for disaster recovery. Local snapshots are stored in the same storage cluster as their source disks for fast backup and recovery of disk data. When disk data is lost, you can use a snapshot to restore the disk data to the point in time when the snapshot was created.

Scenarios

Local snapshots can back up disk data within seconds, which reduces waiting time for business. Local snapshots are applicable to the following scenarios:

  • You can use local snapshots to quickly back up key business systems that contain a large amount of data, such as databases, containers, and SAP High-performance Analytic Appliance (SAP HANA).
  • You can also use local snapshots to back up data before you perform high-risk operations to reduce backup time. High-risk operations include changing system disks, resizing disks, and updating system patches.
  • In common DevOps scenarios, the startup time of ECS instances must be reduced. If you want to clone the environment of an ECS instance, you can use a local snapshot to create a custom image, and then migrate the instance data by copying the image to another region.

Differences between local and normal snapshots

Compared with normal snapshots, local snapshots are created in less time and are stored in a different location for quick disk rollback. The following table describes the differences between local snapshots and normal snapshots.

Snapshot type Storage location Disaster recovery scope Application scope Data synchronization speed Business recovery
Normal snapshot Stored in Object Storage Service (OSS) buckets that are located in the same region as the snapshot Region-level, geo-disaster recovery All disk categories Slow, within minutes Snapshots are used to roll back or create disks to recover data and restore the business.
Local snapshot Stored in the same cluster as the source disk (the disk from which the snapshot was created) Zone-level, zone-disaster recovery Only enhanced SSDs (ESSDs) Fast, within seconds

For more information about snapshot types, see Overview.

Billing

The local snapshot service is commercially available as of July 8, 2020. For information about the billing methods and prices of local snapshots, see Snapshot billing.

Limits

  • You cannot create local snapshots for encrypted enhanced SSDs.
  • A maximum of 10 local snapshots can be retained for each enhanced SSD.
  • You can create local snapshots only for enhanced SSDs.
  • After an enhanced SSD is re-initialized, you cannot use the local snapshots that were created before the re-initialization to roll back the enhanced SSD.
  • After an enhanced SSD that is used as a system disk is replaced, you cannot use its local snapshots to roll back the replacement enhanced SSD.

Related operations

You can use a local snapshot in the ECS console or by calling an API operation. The following table describes the operations that local snapshots support and do not support.
Operation Supported Reference Related API operation
Create a local snapshot Yes. You can create a local snapshot only for an unencrypted enhanced SSD. Create a local snapshot CreateSnapshot
Query the size of a local snapshot Yes. View the snapshot size DescribeSnapshots
Roll back the disk to restore data to the point in time when the local snapshot was created Yes. Roll back a disk ResetDisk
Create another disk from the local snapshot Yes. You can use a local snapshot only to create an enhanced SSD, but the disk size must be equal to the snapshot size. Create a disk from a snapshot CreateDisk
Create a custom image No. N/A N/A
Configure local snapshots to be released along with their source disks No. You can configure only automatic snapshots to be released along with their source disks. N/A N/A
Encrypt local snapshots No. N/A N/A
Use an automatic snapshot policy to create local snapshots automatically No. N/A N/A
Delete a snapshot Yes. We recommend that you delete local snapshots that are no longer needed to maintain a sufficient quota for new local snapshots. Delete a snapshot DeleteSnapshot