How to Measure External Drive Performance Before Purchase

Step by step

1. 1 min

   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.

   Note: An NVMe drive is hardware-limited if plugged into a USB 3.0 port.
2. 2 min

   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.

   Note: Avoid unofficial download mirrors to prevent malware.
3. 1 min

   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.

   Note: Ensure no other high-bandwidth processes are running during the test.
4. 1 min

   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.

   Note: Higher sequential numbers indicate faster transfer speeds for large files.
5. 1 min

   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.

   Note: Standard charging cables often lack the high-speed data pins required for peak performance.