Lesson 053
Storage Systems
Memory hierarchy · HDD vs SSD · caching & locality
1:00How computers layer memory technologies into a hierarchy — from nanosecond registers to millisecond hard disks — and how caching and locality of reference let programs exploit that structure.
By the end, you can
- Recite the five tiers of the memory hierarchy in order of speed and explain the trade-offs at each level.
- Explain why the latency gap between levels matters, using the L1-to-HDD analogy.
- Classify memory tiers as volatile or non-volatile and explain why saving to disk is necessary.
- Describe how an HDD reads data (seek, rotate, read) and why it is slow and shock-fragile.
- Explain NAND flash's page-write/block-erase asymmetry and the role of wear leveling.
- Apply the average-access-time formula (hit% × fast + miss% × slow) to reason about cache effectiveness.
- Distinguish temporal from spatial locality and explain how each is exploited by caches and cache lines.
- Predict whether sequential or random access patterns will produce more cache hits and explain why.
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