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