Benefits and Goals of Multiple Subscriptions in Azure Landing Zones

Azure Landing Zones are a set of guidelines and best practices from Microsoft designed to help users set up a secure, scalable, and compliant Azure environment. One key recommendation within these guidelines is the use of multiple Azure subscriptions as part of the environment setup. This approach has several benefits, aims to accomplish specific goals, and addresses various operational, security, and governance needs. Let's delve into the details:

Benefits and Goals of Multiple Subscriptions in Azure Landing Zones

1. Isolation: Multiple subscriptions can provide isolation between different environments (development, testing, production), business units, or projects. This isolation helps in managing resources more efficiently, reducing the risk of accidental changes or data leaks between environments.

• Environment Isolation: Separate subscriptions for development, testing, and production environments ensure that resources are not accidentally shared or modified across environments. For example, a development subscription can have less restrictive access controls for developers, while the production subscription has strict access controls to protect live data and services.
• Project or Business Unit Isolation: Different projects or business units within an organization can operate within their own subscriptions. This setup allows for custom configurations and ensures that a security breach in one project doesn't compromise another. For instance, a subscription for the HR department can be isolated from the R&D department, protecting sensitive employee data from being accessed by R&D personnel.

1. Cost Management and Billing: By segregating resources into different subscriptions, organizations can achieve more granular cost tracking and billing. This allows for easier attribution of costs to the correct department, project, or budget, facilitating better financial management and accountability.

• Project-Based Billing: By using separate subscriptions for different projects, an organization can directly map Azure costs to specific projects. This is particularly useful for tracking the return on investment (ROI) of individual initiatives or for billing clients in a consulting scenario.
• Departmental Budget Tracking: Separate subscriptions for each department enable precise monitoring and enforcement of budgetary constraints. For example, the marketing department's subscription can have a budget cap set to prevent overspending on Azure resources, facilitating more accurate financial planning and analysis.

1. Limit Management: Azure imposes certain subscription-level service limits and quotas. Distributing resources across multiple subscriptions can help avoid hitting these limits and ensure that deployments can scale without interruptions.

• Avoiding Service Limits: Azure services like Azure Virtual Machines and Azure SQL Database have per-subscription limits. By distributing deployments across multiple subscriptions, an organization can avoid hitting these limits. For instance, if a global company requires thousands of VMs, spreading these across several subscriptions helps bypass the per-subscription VM limit.
• Scaling Workloads: For workloads that need to scale out significantly, such as a multinational application, using multiple subscriptions can ensure that regional deployments can scale without being throttled by subscription-level limits.

1. Access Control and Security: Using multiple subscriptions enables more refined access control policies. Organizations can tailor permissions more closely to the principle of least privilege, minimizing the risk of unauthorized access or actions within the environment.

• Granular Access Control: An organization can grant a developer access to a development subscription without granting them access to the production environment. This minimizes the risk of accidental changes to production resources.
• Enhanced Security Posture: Critical workloads or data can be placed in a subscription with tighter security controls and monitoring, separate from other less sensitive workloads. For example, a subscription holding personally identifiable information (PII) can have additional layers of security monitoring and restricted access, compared to a general testing subscription.

1. Compliance and Regulatory Requirements: Different projects or business units may have varying compliance requirements. Multiple subscriptions allow for customized governance controls that align with specific regulatory standards, making it easier to enforce compliance across different parts of the organization.

• Regulatory Compliance: For businesses operating in multiple regions, having separate subscriptions for each region can help comply with local data residency and sovereignty laws. For example, a European subscription for GDPR compliance and a US subscription for compliance with local regulations.
• Industry-Specific Governance: Organizations in healthcare or finance can have dedicated subscriptions that adhere to industry-specific regulations and standards, such as HIPAA for healthcare data or PCI DSS for payment information, with tailored governance controls and audit trails.

By leveraging multiple subscriptions in these ways, organizations can achieve a high degree of operational flexibility, efficiency, and security, aligning their Azure environment with business needs and regulatory requirements.

Potential Drawbacks of Not Following the Recommendation

• Risk of Resource and Service Limitations: Consolidating all resources into one or two subscriptions might lead to quickly reaching Azure's service limits, potentially hindering the ability to scale resources or deploy new services efficiently.

• Example 1: An organization using a single subscription for all its Azure resources might hit the Compute quota limits when trying to deploy additional Virtual Machines (VMs) for a new project, causing deployment delays and operational issues.
• Example 2: Similarly, Azure Network Service limits could be reached if an organization tries to deploy an excessive number of Network Security Groups (NSGs) within a single subscription, potentially blocking the addition of new services or impacting network security configurations.

• Difficulty in Cost Management and Allocation: With everything in a single subscription, it becomes challenging to track costs and billing accurately for different departments or projects. This can lead to budgeting issues and difficulty in financial reporting.

• Example 1: A company running both development and production environments in the same subscription may find it challenging to distinguish the costs associated with each environment. This can lead to budget overruns in development, impacting the funds available for production resources.
• Example 2: When multiple departments or projects share a subscription, it becomes difficult to allocate Azure costs accurately to each department or project. This lack of granularity in billing can result in disputes over budget allocations and hinder effective financial planning.

• Complexity in Management and Governance: Managing a single or very few subscriptions with a large number of resources can become complex, especially in terms of applying consistent governance policies, compliance checks, and access controls.

• Example 1: Applying governance policies such as tagging strategies or resource naming conventions uniformly across a wide range of resources in a single subscription can become cumbersome. Inconsistencies in applying these policies can lead to governance drift and make resources harder to manage and audit.
• Example 2: With a large number of resources in a single subscription, setting up Role-Based Access Control (RBAC) can become complex and error-prone. This complexity increases the risk of misconfiguring permissions, potentially giving users broader access than necessary, which contradicts the principle of least privilege.

• Increased Security Risks: A lack of isolation between environments or projects increases the risk of accidental or malicious access to critical resources. It can also complicate the process of auditing and securing resources according to best practices.

• Example 1: If development and production environments are within the same subscription, there's a risk that development activities might inadvertently affect production resources, such as by accidentally deleting or modifying a production database, leading to downtime and data loss.
• Example 2: A breach in a low-security area, such as a test environment in the same subscription as high-security production workloads, could provide a pathway for an attacker to escalate privileges and compromise sensitive production resources, highlighting the risks of inadequate isolation.

Conclusion

The use of multiple subscriptions within Azure Landing Zones is designed to provide a more manageable, secure, and scalable Azure environment. It helps organizations to effectively manage costs, enforce governance policies, and ensure operational efficiency. Ignoring this recommendation and consolidating resources into a limited number of subscriptions could lead to management complexities, increased security risks, and challenges in scaling and compliance. Therefore, adopting a multi-subscription strategy is a key component of a well-architected Azure environment.