Redundancy

I posted this to ServerFault.com today. Folks loose site of requirements and systems engineering and it drives me batty. Here was my response to the guys question about redundancy and RAID/COOP/etc. ——– Every design and architecture should be requirements driven. Good systems engineering calls for defining the constraints of the design and implementing a solution that meets that. If you have a SLA with your customers that calls for a .99999, then your solution of N+N redundancy should account for all those LRU (line replaceable units) that could fail. RAID, PS, and COOP planning should all account for that. In addition your SLA with vendors should be the 4 hour response time type or account for a large number of spares onsite. ...