Amazon S3 vs Amazon EBS: Understanding the Key Differences

Introduction

AWS offers multiple storage services, each optimized for specific access patterns, performance requirements, and cost considerations. The two most commonly compared are:

• Amazon S3 (Simple Storage Service) — Object storage for scalable, durable, and low-cost data storage.
• Amazon EBS (Elastic Block Store) — Block storage optimized for high-performance workloads attached to EC2 instances.

Think of it this way: S3 is like a warehouse where you store labeled boxes (objects), while EBS is like a hard drive plugged directly into your computer.

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What is Amazon S3?

Amazon Simple Storage Service (Amazon S3) is an object storage service that offers industry-leading scalability, data availability, security, and performance. It stores data as objects within buckets, where each object consists of the data itself, metadata, and a unique identifier (key).

Key Characteristics of S3

• Storage Type: Object storage
• Access Method: HTTP/HTTPS via REST API
• Scalability: Virtually unlimited — store as many objects as you want
• Durability: 99.999999999% (11 nines) durability
• Availability: 99.99% availability (Standard tier)
• Max Object Size: 5 TB per object
• Access Scope: Accessible from anywhere via the internet
• Pricing: Pay per GB stored + requests + data transfer (starting at ~$0.023/GB-month for Standard)

Common Use Cases for S3

• Data lakes and big data analytics
• Backup and disaster recovery
• Static website hosting
• Media storage and content distribution
• Application log storage
• Archive and compliance data (with Glacier tiers)

S3 Console — Bucket list view showing buckets, regions, and access settings

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What is Amazon EBS?

Amazon Elastic Block Store (Amazon EBS) is a high-performance block storage service designed for use with Amazon EC2 instances. It behaves like a raw, unformatted block device that you can mount on an instance and format with any file system.

Key Characteristics of EBS

• Storage Type: Block storage
• Access Method: Mounted as a volume to an EC2 instance
• Scalability: Up to 64 TiB per volume (varies by volume type)
• Durability: 99.8%–99.999% (depending on volume type)
• Availability: Replicated within a single Availability Zone
• Performance: Low-latency, high-IOPS access (up to 256,000 IOPS for io2 Block Express)
• Access Scope: Attached to EC2 instances within the same Availability Zone
• Pricing: Pay per GB provisioned + IOPS provisioned (starting at ~$0.08/GB-month for gp3)

Common Use Cases for EBS

• Boot volumes for EC2 instances
• Relational and NoSQL databases
• Enterprise applications (SAP, Oracle, Microsoft)
• Throughput-intensive big data analytics engines
• Containerized application storage
• Development and test environments

EBS Console — Volume list showing volume types (gp3, io2, st1), sizes, and attached instances

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Side-by-Side Comparison

Feature	Amazon S3	Amazon EBS
Storage Type	Object storage	Block storage
Access	Via HTTP/HTTPS API from anywhere	Mounted to EC2 instance in same AZ
Max Size	Unlimited (5 TB per object)	Up to 64 TiB per volume
Latency	Higher (milliseconds to seconds)	Very low (sub-millisecond for io2)
Durability	99.999999999% (11 nines)	99.8%–99.999%
Redundancy	Across multiple AZs automatically	Within a single AZ
File System	No file system (objects with keys)	Supports any file system (ext4, xfs, NTFS)
Pricing Model	Pay for what you use	Pay for what you provision
Concurrent Access	Multiple users/applications simultaneously	Typically one EC2 instance (multi-attach available for io1/io2)
Data Modification	Must re-upload entire object	Modify individual blocks in place
Snapshots/Versioning	Built-in versioning	Snapshots stored in S3
Encryption	Server-side and client-side	At-rest and in-transit

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Architecture Differences

How S3 Works

User/Application → HTTPS Request → S3 Endpoint → Bucket → Object
                                                         ↓
                                          Replicated across 3+ AZs

S3 is a standalone service. You don't need an EC2 instance to use it. Any application, user, or service with the right permissions can read and write objects directly via API calls.

How EBS Works

Application → File System → EBS Volume → EC2 Instance (same AZ)
                                    ↓
                     Replicated within the AZ

EBS volumes are tightly coupled to EC2 instances. They appear as local disk drives to the operating system and require an EC2 instance to access the data.

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Cost Considerations

Understanding the pricing model is critical for making the right choice:

S3 Pricing (US East - N. Virginia)

• S3 Standard: ~$0.023/GB-month
• S3 Infrequent Access: ~$0.0125/GB-month
• S3 Glacier Instant Retrieval: ~$0.004/GB-month
• Requests: PUT/COPY/POST ($0.005 per 1,000), GET ($0.0004 per 1,000)
• Data Transfer: Free in, pay for outbound

EBS Pricing (US East - N. Virginia)

• gp3 (General Purpose SSD): ~$0.08/GB-month
• io2 (Provisioned IOPS SSD): ~$0.125/GB-month + $0.065/provisioned IOPS
• st1 (Throughput Optimized HDD): ~$0.045/GB-month
• Snapshots: ~$0.05/GB-month

Key Takeaway

S3 is significantly cheaper per GB for storing large amounts of data, but EBS provides the low-latency performance needed for active workloads. You pay for what you provision with EBS (even if the volume is empty), while S3 charges only for what you actually store.

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When to Use S3 vs EBS

Choose Amazon S3 when you need to:

• Store and retrieve any amount of data from anywhere
• Host static websites or media files
• Build a data lake for analytics
• Store backups, logs, or archives
• Serve content globally (with CloudFront)
• Store objects that are written once and read many times

Choose Amazon EBS when you need to:

• Run a database (MySQL, PostgreSQL, MongoDB, etc.)
• Boot an operating system on EC2
• Perform frequent, low-latency read/write operations
• Use a traditional file system
• Run enterprise applications that require block-level storage
• Process transactional workloads

Can You Use Both Together?

Absolutely! In fact, most AWS architectures use both services together. A common pattern is:

1. EBS for your application's active database and boot volumes
2. S3 for storing backups, logs, static assets, and archived data
3. EBS Snapshots are stored in S3 behind the scenes for durability

Architecture showing a typical web application using both EBS (for databases) and S3 (for static assets and backups)

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Security Features

Both services offer robust security options:

S3 Security

• Bucket policies and ACLs
• S3 Block Public Access
• Server-side encryption (SSE-S3, SSE-KMS, SSE-C)
• VPC endpoints for private access
• S3 Object Lock for WORM compliance
• Access logging and CloudTrail integration

EBS Security

• Encryption at rest using AWS KMS
• Encryption in transit between EC2 and EBS
• IAM policies for volume management
• Snapshot sharing controls
• No public access by design (attached to EC2 only)

S3 Console — Bucket security settings showing Block Public Access and encryption configuration

EBS Console — Volume encryption settings during creation

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Summary

Question	Answer
Need to store files accessible from anywhere?	Use S3
Need a hard drive for your EC2 instance?	Use EBS
Need the cheapest storage per GB?	Use S3
Need sub-millisecond latency?	Use EBS
Need to run a database?	Use EBS
Need to host a static website?	Use S3
Need unlimited storage?	Use S3
Need a boot volume?	Use EBS

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Conclusion

Amazon S3 and Amazon EBS are complementary services, not competitors. S3 excels at storing massive amounts of unstructured data with high durability and global accessibility, while EBS provides the high-performance, low-latency block storage that applications and databases require. Understanding their differences ensures you architect cost-effective, performant, and reliable solutions on AWS.

Pro Tip: When in doubt, ask yourself: "Does my application need to mount this storage like a disk drive, or does it just need to store and retrieve files?" If it's the former, choose EBS. If it's the latter, choose S3.