power management. Specific USB 2.0 chipsets had proprietary methods of achieving SCSI pass-through, which could be used to read S.M.A.R.T. data from drives using tools such as smartctl (using the option followed by "chipset"). More recent USB storage chipsets support the SCSI / ATA Translation (SAT) as a generic protocol for interacting with ATA (and SATA) devices. Using esoteric ATA or SCSI pass-through commands (such as secure-erase or password protection) when a drive is connected via a USB bridge may cause drive failure, especially with the hdparm utility. See also Disk encryption software Media Transfer Protocol Picture Transfer Protocol SCSI / ATA Translation References Further reading From the USB Implementers Forum website: Mass Storage Class Specification Overview 1.4 Mass Storage Bootability Specification 1.0 "Mass Storage Bulk Only 1.0" External links USB Mass Storage Device source code in FreeBSD What actually happens when you plug in a USB device? Linux kernel internals Computer storage buses Computer storage devices Mass storage device class