Local snapshots provide complete copies of disk data at specific points in time and are an important data disaster recovery method. 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 status 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 huge data, such as databases, containers, and SAP HANA.
  • You can also use local snapshots to back up data before you perform high-risk operations to reduce the waiting time for backups. High-risk operations include changing system disks, resizing disks, and updating system patches.
  • In common DevOps scenarios, ECS instances must be quickly started. If you want to clone the environment of an ECS instance, you can use a local snapshot to quickly create a custom image, and then copy the image to migrate the instance data to another region.

Differences between local and normal snapshots

Compared with normal snapshots, local snapshots are stored in a different location, are created within a shorter period of time and provide quicker disk rollback capabilities. The following table describes the differences between local snapshots and normal snapshots.

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

For more information about snapshot types, see Snapshot overview.

Billing

Local snapshots are billed by size on a pay-as-you-go basis . For more information, see Snapshot billing methods.

Operations and limits

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.
Business requirement Supported Reference Related API operation
Create a local snapshot Yes. You can create a local snapshot only for an unencrypted ESSD. Create a snapshot CreateSnapshot
Query the size of a local snapshot Yes View the snapshot size DescribeSnapshots
Roll back the disk to restore data to the status 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 to only create an ESSD and must set the disk size equal to the snapshot size. Create a disk from a snapshot CreateDisk
Create a custom image Yes. You can only use a data disk snapshot to create a custom image. Create a custom image from a snapshot CreateImage
Set local snapshots to be released along with the disk No. You can only set 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 snapshots Yes. You can retain 10 local snapshots for a single ESSD. We recommend that you delete unnecessary local snapshots when the quota is reached. Delete a snapshot DeleteSnapshot