Nikola, > hmm, further checking 4.4.52, it was not really OK too: > > [ 1895.084325] blk_update_request: I/O error, dev sda, sector 239461608 > [ 1895.101099] sd 4:1:1:0: [sda] tag#1 FAILED Result: hostbyte=DID_OK > driverbyte=DRIVER_SENSE > [ 1895.101101] sd 4:1:1:0: [sda] tag#1 Sense Key : Illegal Request [current] > [ 1895.101103] sd 4:1:1:0: [sda] tag#1 Add. Sense: No additional sense information It's the "No additional sense information" that's the problem. Under normal circumstances the drive would return "INVALID COMMAND OPCODE" or "INVALID FIELD IN CDB" in the additional sense data. That would cause us to disable WRITE SAME for the drive in question and report to the block layer that it should zero the blocks manually. However, because we don't get any of the expected sense data back in your case, the failure manifests itself as a generic I/O failure to the stack. And that's why the error is reported up to ext4 instead of the block layer transparently doing fallback zeroing after WRITE SAME has been disabled. What kind of drive is attached to your controller? SATA? SAS? Please send us the output of: sg_inq /dev/sda and sg_vpd /dev/sda Thanks! -- Martin K. Petersen Oracle Linux Engineering