Table of Contents Compare Specs: Our Picks Side by Side The Testbeds We Use to Benchmark Storage Drives The Benchmarks We Use: Internal SSDs The Benchmarks We Use: External SSDs and Hard Drives How We Test Network Attached StorageEach year at PCMag, our experts review dozens of hard drives and solid-state drives (SSDs). Internal M.2 SSDs (PCI Express 3.0 and 4.0) and 2.5-Inch Serial ATA DrivesM.2 drives are internal drives in a "gumstick" form factor. External SSDs and Hard Drives (USB or Thunderbolt)USB 3.2 Gen 2 and Gen 2x2 external drives (which comprise most of the external drives we review these days) are tested on a Windows-based storage testbed housed in a SilverStone tower case. We test external hard drives the same way we do external SSDs, using the same testbeds and benchmark tests, which we'll get into next. Folder Transfer TestOur final test for external drives is a drag-and-drop test, which we also perform on our MacBook Pro.