The hard drives were by Amazon to be well packaged and had the latest firmware, which is also listed on the Qnap Compatibility list. Even the Qnap has the latest firmware.
2014-10-11: 4x 6TB set up as RAID 6, all Prima
2014-10-24: [Hard Disk 1] medium error. Please run bad block scan on this drive or replace the drive if the error persists.
2014-10-24: RAID6 Disk Volume: Drive 1 2 3 4] RAID device in degraded mode ".
Now plate 1 was gone. Bad Block scan performed Raid was built by QNAP HDD on this again.
2014-10-28: [hard disk 2] Medium Error. Please run bad block scan on this drive or replace the drive if the error persists. "
Bad Block scan performed, then again OK.
2014-10-30: [Hard Disk 1] medium error. Please run bad block scan on this drive or replace the drive if the error persists. "
Bad Block scan performed, then again OK on all hard drives.
2014-11-01: [hard disk 2] Medium Error. Please run bad block scan on this drive or replace the drive if the error persists. "
Bad Block scan performed, then again OK on all hard drives.
Very strange: 3 the error occurred exactly at 3:00 clock on the night. The SMART - values are all ok and green.
Now I have to decide in the next day if I every 4 back end or only the two problem disks. Actually I wanted to increase the safety yes - What a bummer. "Never change a running system" works but of course with hard drives, unfortunately, does not last forever ...
**** Update
Although I have returned the plates back, but I change from 1 to 3 stars because
- Two of the four boards ran flawlessly
- The cause (plates or Qnap) is unclear
- WD has super responsive and offered help, see comment.
