The only way you can receive true fail-proof, mission-critical support for your IT production environment is to have a support provider that not only has the skill set to troubleshoot ANY problem but has ALL (100%) of the essential IT hardware in hand. Furthermore, those parts need to be pre-tested before they are ever introduced into your environment.
Customers today have no idea just how exposed their production environment really is when they have their support contracts with the OEM or a typical third-party support provider. They stock only a fraction of the most frequently failed parts locally, which means that if you experienced a failure today, you could be down for days waiting on the correct parts to be delivered. Is this the level of service that you believe you are paying for?