Handle with saving checkpoint failed

If the machine is preemptive, it might be scheduled to be preempted (or encounter other situations that cause the machine to go down). If the checkpoint is being saved at the exact moment, the original data will be corrupted. Therefore, it is reasonable to keep multiple backups locally. Considering the disk space occupancy, it is better to support cloud storage, such as supporting the use of AWS s3.

No files, tests, or entry points are named. Start by locating the checkpoint-saving flow and review how it handles interruption; clarify whether the expected scope is multiple local backups, AWS S3 support, or both, then define completion with tests for recovery and storage behavior.

Written by the indexing model from the issue text.