Free Indexes, queries and scale lessonsIndexes, queries and scale · Stage 0 · Where the data lives · Step 2
The buffer pool
How a cache of pages in memory turns most disk reads into memory reads, and why hit ratio dominates average cost. About 11 minutes.
A system's hit ratio goes from 98% to 99%. Disk reads dominate. What happens to the average page access time?
- AIt roughly halves, because misses are halved
- BIt improves by about 1%
- CIt doesn't change
Show the answer
It roughly halves, because misses are halved. Misses go from 2% to 1%, and the miss term dominates.
4 questions on this idea
Short questions that apply the idea to new cases: trace it, work out a number, put steps in order. A wrong answer explains itself.
Answer them in your browserFree account, no card. Your progress is saved, and the idea comes back in a quick review later.
Sign up free to solve