Idle time = 1.0 – 0.70 = 0.30
3) The Cost of Reliability (and Failure) in Web Servers
Exercises 3 and 4 deal with the cost of not having reliable Web servers. The data is in two sets: one gives various statistics for Gap.com, which was down for maintenance for two weeks in 2005 [AP 2005]. The other is for Amazon.com, which was not down, but has better statistics on high-load sales days. The exercises combine the two data sets and require estimating the economic cost to the shutdown.
The main reliability measure is MTTF. We will now look at different systems and how design decisions affect their reliability. Refer to Figure 1.25 for company statistics.
We have a single processor with an FIT of 200. What is the MTTF for this system?
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