AWS Organizations: A comprehensive guide to multi-account management, consolidated billing, and governance

As AWS usage expands, how to manage multiple AWS accounts has become an important topic. AWS Organizations is a system that streamlines multi-account operations and strengthens governance and cost management. This article provides a detailed explanation of its basic functions, configuration examples, and implementation procedures in a manner that is useful for practical use.

What is AWS Organizations?

AWS Organizations is a service that allows you to manage multiple AWS accounts in an organized manner. It is used as a foundation for multi-account operations because it allows you to consolidate rules and billing on an organizational basis, rather than managing each individual account individually. By creating an organization from the management account and incorporating member accounts, you can maintain overall control while also being able to flexibly operate by department or environment.

AWS Organizations basic functions and positioning

Organizations has three core functions:

1. Accounts can be grouped into organizational units (OUs) and organized by purpose or department, allowing for hierarchical account management across the organization.

2. Consolidated Billing allows you to consolidate all your account usage fees, giving you visibility into costs. You can separate costs by department while still taking advantage of volume discounts.

3. Policy-based control. Service Control Policies (SCPs) allow you to control the range of services and operations that can be used in an account, leading to thorough governance.

These features position Organizations above authentication and authorization management mechanisms such as IAM and AWS Identity Center (formerly AWS SSO).

Background to the need for multi-account management

As AWS usage expands, limitations have emerged in running development, testing, and production all within a single account. Operating without separating environments increases the likelihood of operational errors and resource conflicts, and increases security risks. By adopting a multi-account configuration, you can clearly separate the scope of responsibility for each account and minimize the impact of failures and configuration errors.

There is also a growing need to clearly separate costs by department or project. When combined with consolidated billing, this makes it possible to achieve both departmental cost allocation and overall optimization. From the perspective of audit response and compliance, there is also a need for a system that enforces rules on an account-by-account basis. Organizations is positioned as an essential service for strengthening security, cost management, and governance in response to this background.

Key Features and Benefits of Organizations

Centralized account management

The advantage of being able to centrally manage multiple accounts is that you don't need to log in and configure each account individually; you can define overall policies from the management account and reflect them in each account. Even if your company grows and the number of accounts increases, you can operate efficiently while maintaining control.

Utilizing account grouping (OU: organizational unit)

Organizations allows you to organize accounts into organizational units (OUs). By grouping accounts by department, purpose, or environment (development, testing, production), administrators can apply policies on an OU-by-OU basis, allowing you to flexibly organize accounts while adhering to organizational rules.

Account lifecycle management (new addition/deletion/management transfer)

Organizations also handles lifecycle management, such as automatically creating new accounts and adding them to organizations, inviting and integrating existing accounts, and deleting unnecessary accounts. By setting up delegated administration (Delegated Administrator), you can delegate administrative privileges for some services to specific accounts, which also helps distribute operational load.

Consolidated Billing

You can consolidate the usage fees for multiple accounts and pay them all at once through a management account. You can also visualize the costs for each individual account, making it easy to allocate costs by project or department.

Consolidated billing and cost visibility

Consolidated billing allows you to view billing information for your entire organization on a single dashboard, giving you a clear overview of costs while also allowing you to track departmental breakdowns. This allows accounting and management teams to streamline management of cloud expenses, which can be cumbersome.

Volume discount effect (example of fee discount application)

Another benefit is that volume discounts are applied by combining usage volumes. For example, even if you use EC2 on multiple accounts, the discount is applied based on the combined usage volume. In other words, there is little cost disadvantage even if you separate your accounts, leading to overall cost reductions.

Strengthened governance through Service Control Policies (SCP)

You can use Service Control Policies (SCPs) to control permissions across an entire account. While IAM policies grant and control permissions for users and roles, SCPs define the permission boundaries for an account, and are a mechanism for ensuring governance across the entire organization.

What is SCP?

SCP is a framework that controls "what can be done in this account." Operations outside the scope permitted by the administrator cannot be performed, even if permissions are explicitly granted in IAM. In other words, SCP acts like a "limit setting" for the entire account.

Application pattern example (prohibition/permission rule design)

Typical usage patterns include explicitly prohibiting services that pose a high security risk, restricting usage to specific regions, etc. Conversely, it is also possible to adopt an "allow list method" and design it so that only specified services can be used.

Points to note when implementing SCP

While this is a powerful mechanism, there is a risk that incorrect configuration may prevent administrators from performing necessary operations. For this reason, it is recommended that you first apply it to a limited number of OUs and test accounts, and then confirm the scope of the impact before deploying it to a production environment. It is also important to combine it with audit services such as CloudTrail and Config to continuously monitor the configuration status and violations.

Organizations configuration examples and design patterns

Typical configuration patterns

With Organizations, operational efficiency and ease of governance can change dramatically depending on how you group your accounts. We will introduce three typical patterns.

Simple departmental OU structure

The easiest way to do this is to create OUs by department, such as sales, development, and management. By giving each department an independent set of accounts, it becomes easier to clarify the scope of responsibility. However, since it is difficult to be aware of the environment (production, development, etc.), this can be inflexible if the scope of use becomes large.

OU configuration by environment (production/development/testing)

Another commonly used method is to create OUs for each environment, such as production, development, and testing. By clearly separating the environments, you can eliminate the risk of incorrect operations in the test environment affecting production. This method allows management in line with the system development lifecycle, making it suitable for organizations that prioritize security and stability.

Composite OU configuration (combination of departments and environments)

The most practical approach is the "composite type," which takes into account both departments and environments. For example, by dividing OUs into smaller units such as "Development Department x Production" and "Development Department x Verification," you can ensure both departmental responsibility and environmental classification. This makes the configuration more complex, so it is essential to organize the rules at the design stage.

Design considerations

When considering OU configuration, you need to consider not only short-term operational efficiency but also the impact on long-term scalability and governance.

Basic principles for OU design

Once the OU design is solidified, it is difficult to make major changes later, so it is important to establish basic policies from the beginning. It is necessary to clarify which axes, such as departments or environments, will be prioritized, and to choose a structure that can withstand organizational growth.

Governance/authority design considerations

Assuming that SCP will be applied at the OU level, it is necessary to consider what level of restrictions to impose on each OU. For example, it is effective to differentiate between production OUs by strictly restricting the services available to them and development OUs by allowing more flexible configuration. By considering governance design and OU structure simultaneously, it is possible to achieve both security and efficiency.

Configuration design that takes future expandability into consideration

It is important to design OUs not only to fit the current organizational structure, but also to anticipate the possibility of new departments being added in the future or the need for new environments. Designing OUs with scalability in mind reduces the risk of having to perform major restructuring later.

How to use it with AWS Control Tower and how to use it together

When implementing Organizations, it is important to understand the role of Control Tower and how the two fit together.

Roles and Features of Control Tower

AWS Control Tower is a service that makes multi-account management easy. Building on the functionality of Organizations, it automatically applies best practice guardrails. Because it can be set up via a UI, even those with limited expertise can quickly set up a multi-account environment.

The difference between Control Tower and Organizations

The main difference between the two is the flexibility of control and the degree of freedom of operation. Organizations is designed around an API, allowing for detailed control and automation, while Control Tower provides a standardized setup, but limits the scope of changes that can be made after implementation. In other words, Organizations' strength lies in its high degree of freedom, while Control Tower's strengths are its simplicity and standardization.

Selection and combination examples in practice

For small to medium-sized organizations, it is practical to implement standard multi-account management using Control Tower and then expand it as needed with the additional functions of Organizations. On the other hand, in large-scale environments or cases where strict governance is required, it is common to design the configuration primarily using Organizations, and use Control Tower to assist with initial setup and partial automation.

Organizations installation procedure and initial settings

Enabling and initial configuration of Organizations

First, activate the service using the administrator account. An organization is created around the administrator account, and the entire organization is built by inviting existing accounts to it and creating and adding new accounts. Clarifying the division of roles and naming conventions at the initial stage will make management smoother later on.

Administrative Account Roles

This account oversees the entire organization and performs core operations for Organizations, such as consolidating billing, applying SCPs, creating OUs, etc. Because the administrative account has very powerful privileges, it is recommended that you do not use it for normal business operations, but rather use it exclusively for control and management.

How to join with an existing account

To join an AWS account that you already operate to Organizations, use the invitation system. The management account sends an invitation, and the account's administrator accepts it to join the organization. Through this procedure, you can centrally manage accounts that were previously contracted independently by department.

Creating a new account and setting up automatic addition

You can also create new accounts directly from Organizations, which allows you to efficiently deploy accounts with standardized settings. Having an automatic addition mechanism in place also helps maintain a uniform environment by reducing the need to manually configure each new account.

SCP application process and management

One of the major roles of Organizations is to strengthen governance through SCPs. SCPs are applied to accounts and OUs, and control the scope of operations across the entire organization.

Procedure for creating, applying, and verifying SCP

First, create an SCP from the administrative account and apply it to the OU or account. Then, check that the users and roles with the permissions in IAM can actually perform the operations, and verify that the intended controls are working. If you neglect this verification, there is a risk that operations necessary for business will suddenly become impossible.

Points to note when implementing tests

Because SCP is a powerful mechanism, it is safer to first check its operation on a limited OU or test account rather than immediately applying it to the entire environment. We recommend that you first verify it in a small area and confirm that there are no problems before deploying it to the production environment.

Post-launch management and monitoring

Introducing Organizations is not the end of the process; ongoing operation and monitoring are required. OU changes and account transfers affect governance, so it is essential to proceed in a planned manner and to establish a system for monitoring logs and settings to maintain control.

Change management (impact of OU/account moves)

Changing the OU configuration or moving accounts changes the applicable SCPs and policies. If you perform these changes without checking the impact, necessary operations may be restricted, so it is important to understand the scope in advance and coordinate with the relevant parties before proceeding.

Strengthened monitoring through integration with CloudTrail, Config, etc.

To operate an Organizations environment stably, integration with a monitoring service is necessary. By centrally recording operation history with CloudTrail and tracking resource configuration status with AWS Config, you can quickly detect governance violations and unauthorized operations. Combining these services complements the Organizations control functions and strengthens audit and security responses.

Common issues and points to note when implementing

Service disruption due to incorrect SCP settings

While SCP is a powerful mechanism for controlling the scope of operations across an organization, misconfiguration can make necessary services unavailable. For example, restricting services essential for logging and monitoring can render the security and auditing infrastructure ineffective.

✔Points

SCPs are validated in a test environment and then applied in stages to avoid impacts on the production environment.

Cases where the OU structure is too fixed and flexibility is lost

Dividing OUs too finely makes it difficult to adapt to organizational changes. When new departments or projects are launched, the OUs become more complex and difficult to manage.

✔Points

At the initial design stage, we set standards for the degree of subdivision, and aim for a simple configuration that can be used over the long term.

Balancing account isolation and shared service management

Separating accounts clarifies security and division of responsibilities, but it also creates the issue of complicated management of shared services (network, logs, authentication infrastructure, etc.) Setting up a dedicated shared account is effective, but it can cause problems if dependencies are not properly organized.

✔Points

Incorporate a balance between separation and sharing into your design in advance to clarify the scope of responsibility.

My Feelings, Then and Now

AWS Organizations is a platform that can streamline multi-account operations and strengthen governance and cost management. However, care must be taken to avoid incorrect OU design and SCP configuration, and careful initial configuration planning is essential.

Combining it with Control Tower allows you to achieve both standardization and flexibility. Be mindful of the appropriate use based on the size and requirements of your organization, and proceed steadily from design to operation.