SMART can be wrong / 2018-06-23

Someone brought me a 'WD My cloud' that does not respond at all. So I took it apart and found out how to access the disk in an i386 Linux system: mount the 4th partition as ext4. When the disk was available I did a smart test:

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

But while trying to find out how much data is actually on the disk, I get:

[  866.165641] Sense Key : Medium Error [current] [descriptor]
[  866.165645] Descriptor sense data with sense descriptors (in hex):
[  866.165647]         72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00 
[  866.165659]         b0 90 ea 60 
[  866.165664] sd 2:0:0:0: [sda]  
[  866.165668] Add. Sense: Unrecovered read error - auto reallocate failed

So the disk isn't very healthy. But rerunning the smart check still shows nothing is wrong. It is a Western Digital 'RED' harddisk especially for NAS systems so it should return errors earlier to the operating system but this disk is bad, which is probably related to why the 'my cloud' enclosure isn't working.

Sources used: How to Open a WD My Cloud Case without breaking the tabs, Reading from a Removed Harddrive from WD MyCloud - My Cloud - Personal Cloud Storage / My Cloud - WD Community