What is the difference between Amazon EBS and Amazon S3?

EBS is block storage attached to a single EC2 instance and used like a local disk. S3 is object storage reached over HTTP, independent of any instance, and designed to hold whole files at any scale. They serve different purposes and are often used together in the same architecture rather than as alternatives.

What is the difference between Amazon EBS and Amazon EFS?

EBS attaches to one EC2 instance at a time, like a private disk. EFS is a shared file system that many EC2 instances can mount and use concurrently. Choose EBS when a single instance needs its own disk, and EFS when several instances need to share the same files.

Can an EBS volume be used by more than one EC2 instance at once?

Generally no — a standard EBS volume is attached to a single EC2 instance at a time, which is one of the main things that distinguishes it from Amazon EFS. If multiple instances need concurrent access to the same files, EFS is the appropriate service.

Is Amazon EBS on the AWS certification exams?

Yes — it is introduced on AWS Cloud Practitioner and covered in more depth on AWS Certified Solutions Architect – Associate and AWS Certified CloudOps Engineer – Associate, particularly around choosing between EBS, S3 and EFS and operating volumes day to day. Our /revision library covers that syllabus lesson by lesson.

Cloud services

What is Amazon EBS? A plain-English explainer

By the SaveMyCert Editorial TeamPublished 10 Sept 2026Updated 10 Sept 2026

Amazon EBS (Elastic Block Store) is AWS’s block-storage service: it provides volumes that behave like a hard disk you attach to a single Amazon EC2 instance, so that instance has somewhere to boot from and to read and write data. Like most of the rest of EC2, an EBS volume is created and sized on demand rather than being a fixed piece of physical hardware you had to order in advance, and it can be resized or replaced without touching the server it is attached to. It is the default answer to “where does this virtual server’s disk actually live” on AWS. Here is what block storage means in practice, how EBS is actually used, and how it differs from the other AWS storage services it is most often confused with.

What block storage actually is

Block storage splits data into fixed-size blocks and presents them to a computer as a raw storage volume — the same abstraction a physical hard disk gives an operating system. The operating system then formats that volume with a file system and treats it exactly like a local disk: it can boot from it, install a database on it, or store any files an application needs.

That is a different model from object storage, which stores whole files as “objects” addressed by a key over HTTP rather than as a disk an operating system mounts, and from file storage, which offers a shared folder structure many computers can access at once. Our object-vs-block-vs-file-storage explainer covers all three side by side.

How EBS is actually used

An EBS volume is created and then attached to exactly one Amazon EC2 instance at a time, where it appears to that instance’s operating system as a disk. Most EC2 instances boot from an EBS volume as their root disk, and additional EBS volumes can be attached alongside it for data that needs its own disk — a database’s data files, for example. Our what-is-amazon-ec2 explainer covers the instance side of that pairing.

Because the volume is a separate resource from the instance, it can be detached from one instance and attached to another, resized while still in use, and kept independently of whatever happens to the instance’s compute — within the same constraints AWS documents for doing so.

EBS versus S3: a disk versus an HTTP store

EBS and Amazon S3 solve different problems even though both are “storage”. EBS is a block device attached to one instance, used the way a local disk is used, and only reachable through that instance. S3 stores whole objects, reachable over HTTP from anywhere with the right permissions, independent of any single server. You would not run a database’s live data files on S3, and you would not use EBS to serve files to the public internet — each is built for its own job. Our what-is-amazon-s3 explainer covers the object-storage side in full.

EBS versus EFS: single-instance versus shared

EBS and Amazon EFS are both used with EC2, but the key difference is how many instances can use them at once. An EBS volume is attached to a single instance at a time; if several instances need to read and write the same shared files simultaneously, EBS is the wrong tool. EFS is a shared, elastic file system that many EC2 instances can mount concurrently, which is exactly the case EBS does not cover. Choosing between the two comes down to that one question — does one instance need a disk, or do several instances need to share a file system.

Snapshots and persistence, conceptually

An EBS volume persists independently of the instance it is attached to, so its data survives the instance being stopped. EBS also supports snapshots — point-in-time copies of a volume that can be used to create a new volume or restore data later. This article deliberately does not quote specific durability figures or snapshot pricing, since both are best checked on AWS’s own EBS documentation rather than repeated as a fixed number here.

Where EBS appears in certification study

EBS is introduced as a foundational storage option on AWS Cloud Practitioner, alongside S3 and EFS, so learners can tell the three apart. It goes deeper on AWS Certified Solutions Architect – Associate, which expects you to choose correctly between EBS, S3 and EFS for a given scenario, and on AWS Certified CloudOps Engineer – Associate, which covers day-to-day operational tasks such as resizing, snapshotting and monitoring volumes. Our /revision study library covers that depth lesson by lesson.

Ready to start studying — free?

Original practice questions, timed mock exams and revision notes. No card, nothing to pay.

Jump straight into an exam

CLF-C02 SAA-C03 SOA-C03

Questions, answered

Amazon EBS is used to give an EC2 instance a disk — a block-storage volume it can boot from and read and write data on, the same way a physical server would use a local hard disk. It is typically used for an instance’s root volume and for data that needs dedicated, single-instance storage such as a database’s data files.