Exercise 1: Recommending a RAID Level for a Regeneratable Scratch/Cache Workload — Possible Solution
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Recommended level: RAID 0

Explanation:

The scenario's two defining traits are: (1) raw read/write speed
should be maximized, and (2) the data itself has explicitly no need
for protection, since it can be regenerated at any time if lost. Per
the chapter, "RAID 0... Performance is the best of any level here,
since reads and writes spread across multiple disks in parallel" --
this directly satisfies the first requirement better than any other
level in the chapter, since RAID 0 dedicates 100% of every disk's
capacity and I/O bandwidth to striped data with none reserved for
mirroring or parity overhead.

The chapter is explicit that RAID 0's own real cost is reliability:
"losing any single disk in the array loses all the data -- reliability
actually gets worse than a single disk, not better." For most
workloads this would be a serious problem, which is exactly why the
chapter frames RAID 0 as "only worth it when redundancy already exists
elsewhere... and pure speed matters more than this specific array's
own survival." This scenario is precisely that case: the data is
explicitly described as regeneratable at any time, meaning the
consequence of losing the entire array (which RAID 0 makes a real,
elevated risk) is deliberately low -- there is no unique, unrecoverable
data at stake, only the recomputation cost of regenerating it, which
the team has already accepted as acceptable.

Every other level in the chapter (1, 5, 6, 10) spends some capacity
and/or performance specifically on redundancy this workload doesn't
need, making RAID 0 the level that best matches the stated priorities
rather than paying for protection that provides no real value here.

WHY THIS WORKS AS AN ANSWER
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This selects RAID 0 specifically because the scenario's own stated
tolerance for total data loss (regeneratable data) is the exact
condition the chapter names as the one situation where RAID 0's real
weakness stops mattering, rather than recommending it purely for
speed without addressing the reliability tradeoff.