The goal of availability is to maximize the access and uptime of the designated system and applications – in essence, to make them fault tolerant.
To achieve higher availability there are several key factors which will require particular attention.
Redundancy: Single points of failure should be removed from all areas of the system infrastructure to provide fault tolerance.
Reliability: High quality products should be installed, with the objective of having products with long mean time between failures. Without reliability and redundancy, your system availability will be governed by the weakest link.
Recoverability: This refers to the ability of these systems to fail-over to a hot standby.
Serviceability: Items need to be either quickly repairable or easily swapped out, otherwise you may now have a single point of failure in your system.
Training: Your IT and infrastructure staff should be well trained and exercise their responsibilities and actions following a failure. The same may be said for your key suppliers.
Training staff on day-to-day operations is also vital, as 40% of unplanned downtime is due to human error.
Monitoring: There should be some means of monitoring the ongoing performance of the entire network. Changes in normal performance may indicate a potential failure.
The overall design should be resilient and capable of withstanding individual failures.
The ultimate goal of high availability can be better achieved when accounting for the factors discussed.