S3 vs EBS: what is the difference?
Amazon S3 is object storage accessed over the web and independent of any server, while Amazon EBS is block storage attached to a single EC2 instance like a hard disk — they solve different problems and are not interchangeable. Both are AWS storage services, and both come up constantly in cloud fundamentals, but confusing the two leads to real architecture mistakes, such as expecting a database volume to work like a bucket of files. This guide sets out what each is, the practical differences, and when each one is the right choice.
What each one is, briefly
Amazon S3 stores data as objects — whole files, addressed by a key, accessed over the web via an API — independently of any particular server, and available to anything with the right permissions from anywhere. Our what is Amazon S3 explainer covers the concept in depth.
Amazon EBS provides block storage: a virtual disk volume that attaches to a single EC2 instance, behaving like the internal hard drive of a physical computer. Our what is Amazon EBS explainer covers that concept separately.
The key differences
The practical distinctions that decide between them:
- Storage type — S3 stores whole objects (files plus metadata); EBS stores data at the block level, the way a disk does, which is what an operating system or database engine expects underneath it.
- Access method — S3 is accessed over the web via an API or console, from anywhere with the right permissions; EBS is only accessible by attaching it to the one EC2 instance it is connected to.
- Attachment and scope — S3 is not tied to any server and can be reached independently; an EBS volume is scoped to a single EC2 instance at a time.
- Typical uses — S3 suits files, backups, media and static content; EBS suits an instance’s operating system disk or the storage volume behind a database running on that instance.
- Scalability — S3 scales to hold effectively unlimited objects without you managing capacity; an EBS volume has a size you provision and can resize, but it remains a single volume attached to one instance.
When to use S3
Reach for S3 when storing files, backups, media assets, or building a data lake — anything that needs to be durable, widely accessible and independent of any single server. S3 is also commonly used to host static websites directly, without a server behind them at all.
When to use EBS
Reach for EBS when you need the actual disk behind an EC2 instance — the operating system volume the instance boots from, or the storage volume behind a database or application running on that instance, where the workload expects a conventional block-level disk rather than a web-accessed object store.
Where EFS fits in
There is a third option worth naming: Amazon EFS provides shared file storage that multiple EC2 instances can mount and use at the same time, which neither S3 nor EBS is built for — S3 is not a filesystem, and an EBS volume is tied to one instance. Our what is Amazon EFS explainer covers that case in more depth.
Not always either/or
S3 and EBS are frequently used together within a single architecture rather than as alternatives: an application running on an EC2 instance might use an EBS volume for its operating system and local working data, while storing user uploads, backups or static assets in S3. Each does the job it is built for.
Where this appears in certification study
Distinguishing S3, EBS and the storage types behind them is core material in the AWS Certified Solutions Architect Associate and the AWS Certified Developer Associate, and the basic concepts are introduced in the AWS Certified Cloud Practitioner. The exam-depth detail on configuring either service belongs in our /revision study material.
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