Does a manual snapshot differ from or conflict with an automatic snapshot?

No, both manual and automatic snapshots are copies of the data stored on a cloud disk or on Shared Block Storage at a specified point in time. In this regard, they are neither different from each other nor in conflict with each other.

Why is the size of a snapshot of a disk larger than the disk usage space displayed in the file system?

The simple answer is that data is written is recorder into the snapshot regardless of whether the relevant files have been deleted from file system. For a more detailed answer, see Why is the size of a snapshot of a disk larger than the disk space usage displayed in the file system?

Will the space occupied by the disk be reduced when I delete a file from an ECS instance?

No, when you delete a file from an ECS instance, the file system only tags the file head. This does not reduce the space that the disk occupies.

How can I avoid having my snapshots be automatically deleted by Alibaba Cloud?

This is a problem that is particular to automatic snapshots. To avoid your automatic snapshots from being deleted automatically, you can modify the automatic snapshot policy to change the Keep Snapshots parameter to Always Keep. This way the system will not delete automatic snapshots even if the snapshot quota (by default, 64 snapshots) is reached. However, manual snapshots are different. They are not deleted regardless of whether you have released your disk or instance.

What can I do to delete unnecessary snapshots to reduce backup costs?

The steps you need to take to delete unnecessary snapshots differ between manual and automatic snapshots. For manual snapshots, you can delete unnecessary ones directly. For automatic snapshots, in addition to deleting unnecessary snapshots directly, the system also automatically deletes snapshots, starting with the oldest one, when the snapshot quota (which, by default, is 64 snapshots) specified in the automatic snapshot policy is reached.

Will an automatic snapshot be deleted after I replace the system disk, the instance expires, or the disk is released?

This depends on the settings that you selected when you set the automatic snapshot policy for your automatic snapshots.

  • If you selected Delete Automatic Snapshots While Releasing Disk, then automatic snapshots are deleted automatically by the system in the case that you replace the system disk, the corresponding instance expires, or the disk is released.
  • If you cleared Delete Automatic Snapshots While Releasing Disk, then automatic snapshots are deleted according to the retention duration you have selected. They are not automatically deleted by the system in the case that you replace the system disk, the corresponding instance expires, or the disk is released. You can modify the automatic snapshot policy as needed.

How do I delete a snapshot that I have used to create disks, images, or instances?

Snapshots that you have used to create disks or instances can be directly deleted. However, for snapshots that have been used to create images, you must delete the corresponding image before you delete the snapshot. Otherwise, the snapshot cannot be deleted.

Will the snapshot policy fail to be implemented if I use an automatic snapshot to create a custom image or disk?

No, the snapshot policy will not fail to be implemented.

Can I set multiple automatic snapshot policies for a single disk?

No, you can only have one automatic snapshot policy for a single disk at a time.

Can I use a snapshot of the old system disk to roll back the new system disk after I replace the system disk?

No, you cannot use a snapshot of the old system disk to roll back the new system disk after you replace the system disk.