AWS Organizations is a comprehensive tool for managing multiple AWS accounts, offering simplified billing, security enhancements, and cost optimization through aggregated usage. Here's a detailed summary of the key aspects of AWS Organizations:

AWS Organizations Overview

• Global Service: Enables management of multiple AWS accounts simultaneously.
• Structure:
  • Management Account: The main account in your organization.
  • Member Accounts: Other accounts that join or are created within the organization. Each can only be part of one organization.
• Billing: Consolidated billing across all accounts, providing a single payment method via the management account and potential for pricing benefits from aggregated usage.
• Cost Savings:
  • Shared Reserved Instances and Savings Plans discounts across accounts.
  • Aggregated usage leads to significant discounts on services like EC2 and S3.

Account and Organizational Structure

• Root Organizational Unit (OU): The outermost layer where the management account resides.
• Sub OUs: Can be created for different purposes, such as development, production, HR, or finance, allowing for flexible organization structures.
• Organization by Business Units or Projects: Enables organizing accounts by business units (sales, retail, finance) or projects, offering customization and flexibility.

Advantages of Using AWS Organizations

• Security: Offers better security compared to using single accounts with multiple VPCs due to account separation.
• Cost Management: Enables enforcement of tagging standards for billing and consolidated billing for cost efficiency.
• Centralized Logging and Administration:
  • Automatic enabling of CloudTrail across all accounts.
  • Centralized S3 account for logs and CloudWatch Logs for central logging.
  • Establishment of cross-account roles for administrative purposes.

Security and Compliance

• Service Control Policies (SCPs): IAM policies that can be applied to OUs or accounts to restrict permissions, enhancing security and compliance.
  • Exclusion: SCPs do not restrict the management account to prevent irreversible mistakes.
  • Strategy: Supports both block list and allow list strategies for SCPs, offering flexibility in access and service usage control.

Example Scenario

• Organization Structure: Root OU with sub OUs for HR, Finance, and Prod, containing different member accounts.