What kind of outage is the business trying to protect against? Backup window reduction, planned maintenance, unplanned outages, or site disasters are events to consider when choosing a high availability solution.
Consideration must be given to the types of outages that you are trying to protect your business from.
- Backup window reduction
- In a single system environment, backing up the system is the most common contributor for planned system downtime. As the business need for application uptime increases, the amount of time to backup the data continues to get smaller. A high availability solution can give you the ability to perform offline saves. An offline save is the saving of application data from a backup copy. Each of the data resiliency technologies can offer different benefits for offline saving of data.
- Planned maintenance
- Planned maintenance is the time the system must be down to apply application, software, and hardware upgrades. When planned maintenance can no longer be scheduled around the scheduled working hours, a high availability solution can be implemented to allow for offline maintenance. With offline maintenance, the backup system is upgraded first. After the production environment is switched to the newly upgraded system, the old production system is then upgraded.
- Unplanned outages
- An unplanned outage is an outage that happens during scheduled working hours and can be due to human error, application/software failures, hardware failures, or utility failures and takes down the application environment. The high availability solution can switch the production environment to a backup.
- Site disasters
- A site disaster is typically thought of in terms of a natural disaster, and leads to the requirement of geographic dispersion between the systems in the high availability solution. In addition to natural disasters, there are also events such as chemical spills, terrorist attacks, and city wide loss of power that can impact your business site for a long period of time. The different high availability solutions have different time and distance characteristics. Consideration should be given to recovery time objectives (RTO) and if you need to run normal operations at the remote site, or just a subset of business processes.
Consideration should be given to the amount of disruption a user can tolerate. The application impact can be defined as the following:
- Not an issue. The availability of the application is the primary importance. Performance can be affected as long as availability solution delivers.
- Some performance degradation is acceptable
- Slight degradation in performance
- No perceived performance impact