To get understanding of why cheap USB Flash are cheap and some expensive are expensive. Let’s compare two 32GB flash drives from SanDisk. Cheap one is SanDisk Cruzer 32GB SDCZ36-032G. Expensive one is SanDisk Extreme USB 3.0 SDCZ80-032G.
 |
 |
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| Sequential Read (MB/s) | 16,452 | 91,141 |
| Sequential Write (MB/s) | 3,828 | 76,589 |
| Random Read 512KB (MB/s) | 16,371 | 83,097 |
| Random Write 512KB (MB/s) | 0,548 | 6,252 |
| Random Read 4KB (QD=1) (MB/s) | 2,788 | 10,368 |
| Random Write 4KB (QD=1) (MB/s) | 1,795 | 9,994 |
| Random Read 4KB (QD=32) (MB/s) | 2,693 | 9,12 |
| Random Write 4KB (QD=32) (MB/s) | 0,22 | 2,936 |
| Price (approx.) | 20$ | 40$ |
Speed test done with CrystalDiskMark 3.0.1