When it comes to external storage, very rarely do you deal with random I/O. Since the USB protocol doesn’t acknowledge NCQ, data tends to get written sequentially. However, writing sequentially doesn’t always imply a sequential read. For example, booting Windows 7 off a USB drive involves reading a lot of small bits of information scattered across different logical block addresses, which obviously doesn't happen in the order that data was written to the drive.
So, while it’s not critical, random I/O performance is still an important benchmark to consider. We’re going to focus specifically on 4 KB blocks because, in our experience, it’s the most prevalent transfer size for random I/O. For more information, read page six of Second-Gen SandForce: Seven 120 GB SSDs Rounded Up.
When it comes to testing 4 KB read and writes, we’re bound by the performance of our storage device. Kingston’s HyperX Max 3.0 hits speeds between 10-20 MB/s. So, even when we scale to two devices on the EJ168 and ASM1042, we’re still a long ways off from fully saturating the PCIe x1 lane.
- Should You Care About Your Motherboard's USB 3.0 Controller?
- The Controller Lineup
- Is There A Difference Between USB 3.0 Configurations?
- Test Setup And Benchmarks
- Benchmark Results: Random Read And Writes
- Benchmark Results: 128 KB Sequential Performance
- What Does This Mean In The Real-World?
- Getting Good Speed From USB 3.0