How to Measure External Drive Performance Before Purchase

Validate drive performance before you buy. Learn how to use professional benchmarking tools to ensure your external drive meets your speed requirements.

1. Identify the interface standard. Confirm the drive's connection interface matches your computer's port capability. A USB 3.2 Gen 2 drive requires a compatible 10Gbps port to reach advertised speeds, or it will throttle to 5Gbps. Check your computer's manufacturer specifications to confirm port throughput before testing.
2. Install the benchmarking software. On macOS, download Blackmagic Disk Speed Test from the Mac App Store. On Windows, download CrystalDiskMark from the official developer repository to ensure an untampered binary. These tools provide industry-standard metrics for sequential and random I/O performance.
3. Set the test parameters. In Blackmagic, open the Settings menu and select the target drive as the destination folder. In CrystalDiskMark, select the drive letter under the 'Drive' dropdown menu. Use the default 1GiB test size to ensure the cache is exhausted during the write operation.
4. Run the sequential performance test. Initiate the test by clicking 'Start' or 'All'. Allow the process to complete at least three full cycles to account for thermal throttling. The sequential result represents the speed for large file transfers, such as video editing or disk cloning.
5. Compare results against expectations. Compare the recorded read/write speeds against the manufacturer’s 'up to' specifications. It is normal to see a 10-15% variance due to file system overhead. If the results are 40% lower than advertised, verify that you are using the provided high-speed data cable and not a generic charging cable.