18. S3

S3 (Amazon Simple Storage Service)

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Prerequisites

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1. S3

Amazon S3 (Simple Storage Service) is an object storage service that provides:

• High durability (99.999999999%)
• Scalability (virtually unlimited)
• High availability
• Simple API-based access

👉 In short:

S3 is a storage for files (objects), not servers

1-1. Bucket

• Container for storing objects
• Must have globally unique name

👉 Example:

my-app-images
my-backup-data

1-2. Object

• Actual data stored in S3

• Consists of:

  • File (data)
  • Key (path)
  • Metadata

👉 Example:

Key: images/profile.png

1-3. Key (Path)

S3 doesn’t have real folders 👉 it uses key as virtual path

bucket
 └── images/
      └── profile.png

👉 Actually:

images/profile.png

1-4. Important Characteristics

Durability

• 99.999999999% (11 nines)

Scalability

• Unlimited storage

No server management

👉 No EC2 required

2. How to work S3

Client (App / Browser)
        ↓
      Internet
        ↓
      S3 Bucket
        ↓
    Object Storage

1. Upload file → S3
2. S3 stores as object

3. Access via:

   • URL
   • SDK (C++, Python, etc.)

EC2 / Backend
    ↓
 Download from S3
    ↓
 Load into Memory
    ↓
 Process

2-1. Security

IAM Policy

• Controls access via AWS IAM

Bucket Policy

• Controls public/private access

ACL (Legacy)

• Old method (not recommended)

2-2. Real Use Cases

Static Website Hosting

• HTML / CSS / JS hosting
• Often combined with CloudFront (CDN)

Image / Video Storage

• Profile images
• Media files

Backup & Logs

• DB backup
• Server logs

Data Pipeline

• Used with Lambda / Athena

2-3. Storage Classes

Class	Use Case
Standard	Frequently accessed
Intelligent-Tiering	Auto optimize cost
Standard-IA	Infrequent access
Glacier	Archive
Glacier Deep Archive	Long-term backup

3. How to create S3

3-1. Search S3

3-2. Click Navigation pane → “General purpose buckets”

3-3. Click Button → “Create bucket”

3-4. Step 1. General Configuration

3-5. Step 2. Security

1. Object Ownership: Controls who owns objects in the bucket

   • Options:
     • Bucket owner enforced (Recommended) → ACLs disabled, bucket owner owns everything
     • ACLs enabled → Object uploader can own objects

2. Block Public Access: Prevents public access to bucket and objects

   • Options:
     • Block all public access (Recommended) → No public access allowed

3. Bucket Versioning: Keeps multiple versions of the same object

   • Options:
     • Disable → Only latest version exists
     • Enable → Stores all versions

3-6. Step 3. Security

3-7. Upload Data

4. S3 vs EBS vs EFS

Feature	S3	EBS	EFS
Type	Object	Block	File
Attach to EC2	❌	✅	✅
Access	HTTP	OS disk	Network FS
Use case	File storage	OS / DB	Shared storage