I'm getting the following error message when running hdparm -S on my external USB hard drive:

SG_IO: bad/missing sense data

Where is this sense data stored on the hard drive? I never encountered this error before, so I'm assuming something on the drive went corrupt.

  • 1
    Here is a good explanation of the issue you're having:Hard Drive error: bad/missing sense data
    – galoget
    Jan 31, 2018 at 4:24
  • @galoget That answer makes it seem it's a hardware issue ("drive controller doesn't support that method of enquiry, not all usb sata chipsets are created equal"). As I said in my question, hdparm -S worked before with the hard drive, but only now does it return the "SG_IO: bad/missing sense data". Did my hardware go bad?
    – Geremia
    Jan 31, 2018 at 16:03

2 Answers 2


hdparm is communicating with the driver controller firmware. It is requesting the sensor data from there. Here it might be that the controller/firmware does not support this command/operation or the tool is not the right for your controller/firmware.

If interested in more background information and details you may follow up at Linux SCSI Generic (sg) Driver, Python-SCSI or t10.org.

  • I did encounter the issue after upgrading my Linux kernel (I think to 4.14.14 or 4.14.15), so maybe it is the sg driver that changed.
    – Geremia
    Jan 31, 2018 at 16:05

The issue was that I needed to use:

sdparm -rs SCT=600 /dev/my_disk
sdparm -rC stop /dev/my_disk

instead of

hdparm -S 12 /dev/my_disk
hdparm -y /dev/my_disk


(courtesy this table of sdparm's equivalents of hdparm commands)

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