Author wasn't able to get stable test results with two or more simultaneous tests.
Verification in linear mode – fastest way to determine if your drive needs data rescue, has recoverable errors or in its perfect shape.USB Flash (pen drives) – surface tests only.RAID volumes made of ATA (IDE) / SATA / SCSI HDDs (surface tests only).FireWire or IEEE 1394 HDD (see Appendix A).External USB drives and all major USB boxes (see Appendix A).