Reasons For Unavailability
A survey among academic availability experts in 2010 ranked reasons for unavailability of enterprise IT systems, from most to least important, as follows:
| Causal factor of unavailability |
|---|
| Lack of best practice change control |
| Lack of best practice monitoring of the relevant components |
| Lack of best practice requirements and procurement |
| Lack of best practice operations |
| Lack of best practice avoidance of network failures |
| Lack of best practice avoidance of internal application failures |
| Lack of best practice avoidance of external services that fail |
| Lack of best practice physical environment |
| Lack of best practice network redundancy |
| Lack of best practice technical solution of backup |
| Lack of best practice process solution of backup |
| Lack of best practice physical location |
| Lack of best practice infrastructure redundancy |
| Lack of best practice storage architecture redundancy |
The factors themselves are based on the work of Evan Marcus and Hal Stern.
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