S3 vs EBS
Compare object storage with block storage in AWS.
Storage
Amazon S3
Amazon S3 is an object storage service used for files, backups, archives, logs, static assets, and durable cloud storage at massive scale. It is accessed through APIs, not as a normal block device.
Storage
Amazon EBS
Amazon EBS is block storage for EC2 instances. It behaves like a virtual disk attached to compute and is commonly used for operating system volumes, databases, and persistent instance storage.
Key Differences
S3 is object storage accessed over APIs, while EBS is block storage attached to EC2 instances.
S3 is designed for massive durability and scale, while EBS is designed for low-latency disk-like access from compute.
EBS behaves like a mounted volume for an instance, while S3 behaves like a storage service for objects and files.
S3 is not a normal filesystem disk, while EBS is used like a virtual hard drive.
EBS is tied to instance and availability zone design choices, while S3 is region-level object storage.
S3 is ideal for static and durable storage, while EBS is ideal for application and operating system storage attached to compute.
When to Use
When to use S3
Use S3 for backups, static files, archives, application assets, logs, data lakes, and any scalable object-storage use case.
When to use EBS
Use EBS when an EC2 instance needs persistent block storage for its operating system, application data, or a database workload.
Tradeoffs
S3 is highly scalable and durable, but not suitable as a low-latency attached disk.
EBS is excellent for block storage on compute, but less flexible and less scalable as a general object storage platform.
S3 solves storage-at-scale problems, while EBS solves attached compute storage problems.
Common Mistakes
Thinking S3 is just a cheaper EBS replacement.
Trying to use S3 like a normal disk volume for applications that expect block storage.
Ignoring the architectural difference between object access and attached block storage.
Interview Tip
A strong short answer is: S3 is object storage, EBS is block storage for EC2.