Chapter 3 of the book talks about the trade-offs of using low-end servers and high-end servers. The text argues that we don't need a server that's too high-end, because the price per performance is too high according to the TPC-C benchmark. In addition to that, slower CPUs are generally more power efficient and thus, you won't need as much cooling system if the datacenters are being build using a lower-end servers (Thus, slower CPU). However, the text continues and state that we don't want a server that's too low because there may be the need to spend a substantial amount of effort to parallelize the code to meet the requirements. Thus, a middle ground that takes the best of both worlds are needed.
Chapter 4 of the book talks about the power consumption of datacenter and the characteristics of its cooling systems. The low-voltage power typically enters the datacenters through Uninterruptible Power System (UPS) systems that also conditions the incoming power to remove abnormalities such as voltage spikes. Then, the text talks about the various techniques that could be utilized for cooling systems. For example, one technique is called in-rack cooler which adds an air-to-water heat exchanger at the back of a rack so that the hot air exiting the servers immediately flows over coils cooled by water. These techniques are very important since datacenters generate a lot of heats.
Chapter 7 of the book talks about failures and repairs in the WSCs. Since hardware failures happens all the time (as the book says, MTBF of 30 years per computer typically results in 1 failure per day in servers), software must be fault-tolerant. The typical cause of failures for WSCs are due to bad network connectivities, application faults and system software faults. It's rarely due to faulty firmwares or kernels. The book then goes on to argue that cheaper hardware generally means that it breaks more often and the cost of reapiring them may even offset the hardware price.
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