What does "Sense Key : Recovered Error" mean?

Question

When powering up a external USB 2TB drive on CentOS 6.4 and I am seeing these messages in the dmesg output:

kjournald starting.  Commit interval 5 seconds
EXT3-fs (sde1): using internal journal
EXT3-fs (sde1): mounted filesystem with ordered data mode
sd 10:0:0:0: [sde] Sense Key : Recovered Error [current] [descriptor]
Descriptor sense data with sense descriptors (in hex):
        72 01 04 1d 00 00 00 0e 09 0c 00 00 00 00 00 00 
        00 4f 00 c2 00 50 
sd 10:0:0:0: [sde] ASC=0x4 ASCQ=0x1d
sd 10:0:0:0: [sde] Sense Key : Recovered Error [current] [descriptor]
Descriptor sense data with sense descriptors (in hex):
        72 01 04 1d 00 00 00 0e 09 0c 00 00 00 00 00 00 
        00 4f 00 c2 00 50 
sd 10:0:0:0: [sde] ASC=0x4 ASCQ=0x1d

What does "Sense Key : Recovered Error" mean? I gather it has recovered from something, but how do I find out the source of this problem? Is there anything I should do to follow-up this? It mounts without a problem and I was able to do an rsync backup to it without any complaints. Thanks!

Answer 1

This is believed to be caused by a benign defect in the USB controller that the hard drive uses. Note that this is not actually an error code but an "abnormal success" code. This means the operation was successful, and the kernel knows it completed successfully, but the controller reports for informational purposes that it had to retry the operation or otherwise found something unusual about the execution of it. This is not believed to reflect any problem with the drive medium.