Numbers To Know medium
Roughly how much slower is reading 1MB sequentially from SSD vs reading from RAM?
- A approximately 2x slower
- B approximately 1,000x slower due to microsecond-level seek times
- C approximately 10x to 20x slower based on sequential throughput
- D approximately 1 Million x slower
Answer: C. approximately 10x to 20x slower based on sequential throughput
When discussing storage speeds, it is vital to distinguish between *random* access and *sequential* throughput. While an SSD is thousands of times slower than RAM for random lookups, the gap shrinks significantly for large sequential reads. Modern RAM provides ~20-50 GB/s, while high-end NVMe SSDs reach ~3-7 GB/s, making the SSD only about 10-20x slower in this specific scenario. Engineering for sequential I/O (often through techniques like log-structured storage) allows systems to leverage the massive capacity of SSDs while maintaining high throughput that isn't too far behind raw memory speeds.
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