Identify Infrastructure Qualities
VMware named five infrastructure qualities: Availability, Manageability, Performance, Recoverability and Security. If you are familiar with other design methodologies you might have encountered other terms, but here i want to describe the VMware terms.
Availability is the ability of a system or service to perform its required function when required. It is usually calculated as a percentage like 99,9%.
Manageability describes the expense of running the system. If you have a huge platform that is managed by a tiny team the operational costs are very low.
Performance is the measure of what is delivered by a system. This accomplishment is usually measured against known standards of speed completeness and speed.
Recoverability describes the ability to return a system or service to a working state. This is usually required after a system failure and repair.
Security is the process of ensuring that services are used in an appropriate way.
Lets take a website for example. To understand how to compare your design against this requirements you could ask yourself:
- Availability: Is website up and running?
- Manageability: How expensive is it to keep the system up?
- Performance: How fast does the webserver responds?
- Recoverability: If the server crashes, how fast can it be restored?
- Security: Are the customers data safe?
Redundancy and Single Point of Failure
A single point of failure is a component of a system that, if it fails, will cause the entire system to fail. Systems can be made robust bei adding redundancy. A server usually attains internal component redundancy by having multiple hard drives, network connections or power supplies. By having multiple servers attached to a cluster you can archieve server hardware redundancy.
VMware Availability Services
vSphere High Availability (HA) minimizes your downtime by restarting virtual machines on remaining hosts in case of hardware failures.
vSphere Fault Tolerance (FT) provides continuous availability for virtual machines by creating a live copy of a virtual machine to another physical host.
Differentiate Business Continuity and Disaster Recovery
Business Continuity is focused on avoiding or mitigateing the impact of a risk. (Proactive)
Disaster Recovery is focused on how to restore the services after a outage occurs. (Reactive)
VMware offers a course about disaster recovery and business continuity. It is free at the moment, so check it out:
DRBC Design - Disaster Recovery and Business Continuity Fundamentals
VCAP5-DCD Exam Blueprint v1.1
- Understand what logical availability services are provided by VMware solutions.
- Identify and differentiate infrastructure qualities (Availability, Manageability, Performance, Recoverability, Security)
- Describe the concept of redundancy and the risks associated with single points of failure.
- Differentiate Business Continuity and Disaster Recovery concepts.
Skills and Abilities
- Determine availability component of service level agreements (SLAs) and service level management processes.
- Explain availability solutions for a logical design based on customer requirements.
- Define an availability plan, including maintenance processes.
- Prioritize each service in the Service Catalog according to availability requirements.
- Balance availability requirements with other infrastructure qualities
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