I have an external USB-drive which is giving me the following output on running the command $ smartctl /dev/sdb -Hon it: SMART Status not supported: Incomplete response, ATA output registers missingSMART overall-health self-assessment test result: PASSED Warning: This result is based on an Attribute check. Could you elaborate if this is something to worry about or if it is just a wrong setting? Generally, what is the meaning of the health status in simplified form? Maybe as a relevant aside: The short and long tests finish without issues.
SMART health-test and status
hard disk;smartctl;smart
I haven't seen this kind of warning you've got, yet. But apparently it means that smartctl only evaluated the attribute table (see below) because there is no further information from SMART explicitly about the health which is typically a part of the ATA protocol. The response overall is considered not reliable in this case by the author of smartmontools. Drives attached directly to a SATA controller work better with SMART from what I've seen so far.As concerns the attribute table, when you take a look at a SMART attribute output with smartctl -A /dev/XXX, you'll see three columns VALUE, WORST and THRESH. Here a part of such an output:ID# ATTRIBUTE_NAME     FLAG   VALUE WORST THRESH TYPE   UPDATED WHEN_FAILED RAW_VALUE  1 Raw_Read_Error_Rate   0x002f  200  200  051  Pre-fail Always    -    0  3 Spin_Up_Time      0x0027  189  182  021  Pre-fail Always    -    5508  4 Start_Stop_Count    0x0032  100  100  000  Old_age  Always    -    18The first column VALUE tells you the current value of the attribute. The WORST column tells you the worst (typically lowest) value SMART has ever seen. The THRESH column tells you what the vendors considers as lowest possible value considered as healthy.If the WORST column shows values below THRESH in same row, the drive is considered as not healthy. It also implies that VALUE has been seen below THRESH, of course. You can also see that only the attributes of type Pre-fail matter when evaluating health. Other thresholds are simply set to 0 and their attributes cannot fail.This table is all that smartctl used for the analysis of the drive's health. And it is not really the correct way to do it right.