High availability is a characteristic of a system, which aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period.
For example, hospitals and data centers require high availability of their systems to perform routine daily activities. Availability refers to the ability of the user community to obtain a service or good, access the system, whether to submit new work, update or alter existing work, or collect the results of previous work. If a user cannot access the system, it is - from the users point of view - unavailable.
- Elimination of single points of failure. This means adding redundancy to the system so that failure of a component does not mean failure of the entire system.
- Reliable crossover. In redundant systems, the crossover point itself tends to become a single point of failure. Reliable systems must provide for reliable crossover.
- Detection of failures as they occur. If the two principles above are observed, then a user may never see a failure.
Availability is usually expressed as a percentage of uptime in a given year. The following table shows the downtime that will be allowed for a particular percentage of availability, presuming that the system is required to operate continuously. Service level agreements often refer to monthly downtime or availability in order to calculate service credits to match monthly billing cycles. The following table shows the translation from a given availability percentage to the corresponding amount of time a system would be unavailable.
Knowing which IT assets you have and how they are used has become a challenge in today's complex and ever evolving IT infrastructure, yet managing IT Assets is an important task for any business. A typical IT infrastructure has many different assets of various types, and new IT projects are deploying additional assets to support the business objectives. These challenges includes tracking IT assets across multiple offices and IT platforms, detecting software installed and used, and discovering new devices that are on the network.
- Life cycle management
- Replacement through change control process of existing in-scope assets at end of useful life or support manufacture
- For base service asset life is typically five years
- Maintenance and management of all assets in a global database