S3 vs EBS

Overview

Amazon S3 and Amazon EBS are both AWS storage services, but they are different kinds of storage for different jobs. S3 is object storage accessed over the network through an API. EBS is block storage that attaches to an EC2 instance like a physical disk. Confusing the two leads to poor architecture, so understanding the distinction is essential.

Key Differences

S3 stores data as objects in buckets, each retrieved by key over HTTP. It is virtually unlimited in capacity with no provisioning, and it offers extremely high durability, designed for eleven nines by replicating data across multiple Availability Zones. S3 is accessible from anywhere with the right permissions, which makes it ideal for files, backups, media, logs, static website assets, and data lakes. It is not a filesystem and cannot serve as a boot disk, and individual object requests have higher latency than local block access.

EBS provides block storage volumes that attach to EC2 instances and behave like disks. You can format them with a filesystem, use them as boot volumes, and run databases on them. EBS delivers low-latency, high-IOPS performance suitable for transactional workloads. Volumes are provisioned with a chosen size and performance level and are replicated within a single Availability Zone for durability. A standard volume attaches to one instance at a time, though multi-attach options exist for certain volume types.

The core distinction is object versus block. S3 is for large-scale, network-accessible, unstructured data. EBS is for low-latency disk storage tied to compute.

When to Choose S3

Choose S3 for storing files, backups, media, logs, and any large volume of unstructured data, and for content that must be reachable over the network by many clients. It is the foundation for data lakes and static asset hosting, offering near-infinite scale and exceptional durability without capacity planning.

When to Choose EBS

Choose EBS when an EC2 instance needs a disk: for boot volumes, filesystems, and databases that require low-latency, high-IOPS block access. It is the right choice for stateful workloads running on a specific instance that demand consistent disk performance.

Verdict

S3 and EBS are complementary, not competing. Use S3 for scalable, durable, network-accessible object storage and EBS for low-latency block storage attached to compute. Many architectures use both: EBS for the instance's working disk and databases, S3 for backups, media, and analytics data. Pick based on whether you need object storage over the network or block storage on a disk.