EBS Snapshots – Detailed Overview | Notion

What is an EBS Snapshot?

An EBS Snapshot is a point-in-time backup of your Amazon Elastic Block Store (EBS) volume.
Snapshots are stored in Amazon S3, but managed automatically by AWS (you don’t access them as S3 objects).
They are incremental, meaning only the blocks that have changed since the last snapshot are saved, reducing cost and time.

Key Features

Feature	Description
Incremental Backups	Only changed data blocks are stored after the first full snapshot.
Durable Storage	Stored redundantly across multiple Availability Zones using Amazon S3.
Restoration	You can create a new EBS volume from any snapshot.
Cross-Region Copy	Snapshots can be copied to other AWS Regions for disaster recovery.
Cross-Account Sharing	Snapshots can be shared with other AWS accounts or made public (if needed).
Encryption Support	If the source volume is encrypted, snapshots are automatically encrypted.

How Snapshots Work

Initial Snapshot
- First snapshot of a volume is a full backup — all blocks are stored.
Subsequent Snapshots
- Each later snapshot saves only modified blocks since the last snapshot.
Storage
- AWS maintains a reference chain between snapshots to restore complete data when needed.
Restoration
- You can create a new volume from any snapshot; AWS reconstructs full data automatically.

Example Scenario

You have an EBS volume /dev/xvdf of 100 GiB attached to an EC2 instance.
You take a snapshot every day.
- Day 1 snapshot: full backup (100 GiB).
- Day 2 snapshot: only changed blocks (~10 GiB).
- Day 3 snapshot: another incremental backup (~5 GiB).
If you restore from Day 3, AWS combines all prior snapshot data transparently to recreate the full volume.

Diagram (Text Description)