Red Hat ENTERPRISE LINUX 3 - INTRODUCTION TO SYSTEM ADMINISTRATION Administration Manual page 159

Chapter 8. Planning for Disaster
8.1.1.1.3. Spares That Are Not Spares
When is a spare not a spare? When it is hardware that is in day-to-day use but is also available to serve
as a spare for a higher-priority system should the need arise. This approach has some benefits:
Less money dedicated to "non-productive" spares
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The hardware is known to be operative
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There are, however, downsides to this approach:
Normal production of the lower-priority task is interrupted
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There is an exposure should the lower-priority hardware fail (leaving no spare for the higher-priority
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hardware)
Given these constraints, the use of another production system as a spare may work, but the success of
this approach hinges on the system's specific workload and the impact the system's absence has on
overall data center operations.
8.1.1.2. Service Contracts
Service contracts make the issue of hardware failures someone else's problem. All that is necessary
for you to do is to confirm that a failure has, in fact, occurred and that it does not appear to have a
software-related cause. You then make a telephone call, and someone shows up to make things right
again.
It seems so simple. But as with most things in life, there is more to it than meets the eye. Here are
some things that you must consider when looking at a service contract:
Hours of coverage
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Response time
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Parts availability
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Available budget
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Hardware to be covered
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We explore each of these details more closely in the following sections.
8.1.1.2.1. Hours of Coverage
Different service contracts are available to meet different needs; one of the big variables between
different contracts relates to the hours of coverage. Unless you are willing to pay a premium for the
privilege, you cannot just call any time and expect to see a technician at your door a short time later.
Instead, depending on your contract, you might find that you cannot even phone the service company
until a specific day/time, or if you can, they will not dispatch a technician until the day/time specified
for your contract.
Most hours of coverage are defined in terms of the hours and the days during which a technician may
be dispatched. Some of the more common hours of coverage are:
Monday through Friday, 09:00 to 17:00
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Monday through Friday, 12/18/24 hours each day (with the start and stop times mutually agreed
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upon)
Monday through Saturday (or Monday through Sunday), same times as above
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