The WD Desktop drives (Green/Blue/Black) are not recommended for RAID volume usage, as the following issues has been realized.
1. Slow performance
2. Disk drop out from RAID easily
3. Read/write error on file system
According to the reply from WD manufacturer.
Q:Are WD Desktop drives (Green/Blue/Black) good for RAID systems?
A:You may need to know if the NAS controller works with drive that have the TLER disabled, or the TLER needs to be enabled on the drive. However, we do support these drive on computers only, but not on RAID environment, please see the RAID enabled drives in the link below: (Enterprise Drive) http://www.wdc.com/en/products/index.asp?cat=2
We have add the WD Desktop drives as the not suggested HDD on HDD compatibility List
The HDDs have passed QNAP lab's initial verification of compatibility. However, because the HDD manufacturer has suggested not to use the desktop HDDs in RAID subsystems and some users have reported unstable experience with these HDDs, we do not recommend using these HDDs with QNAP products."