Why is my AMI or EBS snapshot creation slow or stuck in the Pending state?

Resolution

Changed blocks

The first snapshot of any volume is always a full snapshot. The snapshot contains the data blocks that are written to the volume after its creation. Subsequent snapshots are incremental snapshots that only contain changed data blocks written to the volume after the last snapshot.

If there are no available snapshots for a write-intensive volume, then the number of blocks that you must copy as part of a full snapshot is greater. If you change more blocks after the last snapshot, then subsequent snapshots take longer to complete. For more information, see Why is my incremental EBS snapshot taking the same time to create as a full EBS snapshot?

To resolve this issue, take the following actions:

• To reduce the number of changed blocks in between subsequent snapshots, frequently create snapshots.
• Use Amazon Data Lifecycle Manager to automate snapshot creation, retention, and deletion.
• Set the snapshot frequency based on your Recovery Point Objective (RPO).

Note: EBS snapshots are charged for the incremental data saved in Amazon Simple Storage Service (Amazon S3), not the number of snapshots. For more information, see Amazon EBS pricing.

Multivolume snapshots stuck at 99%

When you create simultaneous backups of multiple EBS volumes attached to an Amazon Elastic Compute Cloud (Amazon EC2) instance, the snapshots progress independently. However, they complete together.

The entire set remains at 99% until all snapshots are complete. After the final snapshot completes its backup, all snapshots in the set automatically move to the Completed state.

You don't need to take any action when snapshots are at 99%. The process automatically completes when all snapshots finish.

Stacked snapshots

Stacked snapshots occur when you create multiple snapshots for the same volume in a short time.

The first snapshot starts creation, and then additional snapshots move to the Pending state at 0%. The additional snapshots don't progress until the first snapshot completes.

Note: When you delete a pending snapshot, you don't stop the creation process. The snapshot completes its creation process before it deletes.

To resolve this issue, don't create new snapshots when snapshot creation is in progress. Then, wait for current snapshots to complete before you create new ones.

Related information

Why does my Amazon EBS snapshot show no progress or shows the error, "ConcurrentSnapshotLimitExceeded"?

Guidelines and best practices for archiving Amazon EBS snapshots