Architectural Consideration for DR in Cloud Computing

To take full advantage of the benefits of Cloud computing, there are a number of architectural implications that should be observed.
Business Architecture
Cloud offers unprecedented control in allocating resources dynamically to meet the changing needs of a business. This is only effective when the businesses service level objectives have been clearly articulated and guide the cloud’s enterprise management layer. Application performance metrics and SLAs must be carefully documented and monitored for an effective cloud deployment.
To maximize the distributed capabilities afforded by clouds, business processes should identify areas where asynchronous or parallel processes can be used.

Key Business Architectural Principles
• Business Alignment, Cost Optimization
• Compliance with Laws and Regulations
• Business Agility
• Minimize Cost
Application Architecture
Application services should abstract resource allocation and avoid the tight binding of its resources to invokers of the service. Dependencies on static references to infrastructure (for example, storage, servers, network resources), as well as tightly coupled interfaces to dedicated systems, should be avoided.
To take advantage of the cloud’s scalability capabilities, applications should take advantage of distributed application design and utilize multi-threading wherever possible. Applications should leverage distributed locking, GUID generation, and integration layers to provide the greatest flexibility in deploying on a cloud.
Key Application Architectural Principles
• Technology Independence, Adherence to Standards
• Common Development Methodology
• Loosely coupled Interfaces.
Information Architecture
Cloud computing offers the potential to utilize information anywhere in the cloud. This increases the complexity associated with meeting legal and regulatory requirements for sensitive information. Employing an Information Asset Management system provides the necessary controls to ensure sensitive information is protected and meets compliance requirements. This is essential when considering public or hybrid clouds as information may leave the confines of the data center, which may violate certain legal and regulatory requirements for some organizations.
Key Information Architectural Principles
• Implement Information Lifecycle Management
• Regulatory and Legal Compliance
• Enforce Data Privacy.
Technology Architecture
Implementing Service Oriented Architectures (SOA) provides the most effective means of leveraging the capabilities of cloud computing. SOAs distributed nature, service encapsulation; defined service level objectives, virtualized interfaces, and adherence to open standards align with Cloud’s architectural requirements.

Cloud’s highly distributed nature requires a more robust security management infrastructure. Implementing federated identity hubs and defined communication zones are typically required for cloud deployments to control access across multiple cloud nodes--especially when those nodes exist outside the organization.
Cloud infrastructures simplify the deployment of grid application servers which offer improved scalability and disaster recovery.
Key Technology Architectural Principles
• Control Technical Diversity
• Adherence to Standards
• Scale Capacity and availability to satisfy Business Objectives
• Virtualize dependencies to hardware and software
• Unified Security Infrastructure.
Organizational Considerations
The successful deployment of clouds within organizations depends on a number of factors--some technical and others organizational. These include:
• The extent of infrastructure standardization among the existing application silos of the current state architecture
• The complexity and degree of customization and integration of the current state architecture.
• The willingness of lines-of-business to share infrastructure instead of “owning their own”
• The extent to which the current state architecture must accommodate legacy systems
• Past experience of the IT department in deploying technologies and concepts critical for clouds, such as standardization, consolidation, virtualization, clustering, and more
• An effective governance structure is required to guide the cloud implementation to meet the business objectives of the organization.



System Architecture Design Considerations
Performance Considerations
• Cloud infrastructures have the potential to introduce unpredictable performance behaviors. While sharing a large infrastructure can average out the variability of individual workloads, it is difficult to predict the exact performance characteristics of your application at any particular time. Like any shared infrastructure, varying individual workloads can impact available CPU, Network and Disk I/O resources resulting in unpredictable performance behavior of the combined applications.
• Public cloud infrastructures by the nature that they are outside the enterprise data center must leverage wide area network which can introduce bandwidth and latency issues. Multi-peered networks, encryption offloading, and compression are necessary design considerations.
• In addition, many Public Cloud providers have multiple storage offerings with varying performance characteristics. Typically, write performance is typically impacted to a much larger degree than read performance, especially with non-block oriented storage.
• Variability in network resources can significantly impact write operations with clustered application servers. Applications should categorize information that has lower availability requirements to identify candidates for asynchronous writes or replication.
• To overcome many of these challenges, Cloud can leverage proactive scaling of resources to increase capacity in anticipation of loads. For example, if you have implemented a web site that has heavy loads from 9:00 am to 3:00 pm, you can dynamically increase capacity for that period of time. To take advantage of this, your application must be architected to leverage distributed application design.