Note1
Western Digital, the YS series is known to drop out from RAID sets intermittently. Western Digital has posted a firmware update that fixes this. If you met this problem, you may upgrade your HDD firmware via http://support.wdc.com/download/?cxml=n&pid=15&swid=57
Any further question, you may refer here for reference.

Note2
Due to the height of Maxtor 200 GB (6L200M0) & 250 GB (6L250S0) HDD SATA connector is a little bit different from the TS-101 connector, it may cause TS-101 connector broken when installing.

Note3
When using this hard drive model with the TS-119, the hard drive temperature will be slightly higher.

Note4
As suggested by certain HDD providers, the hard drives of the same brand and series are collectively recognized as compatible with QNAP products if the largest-capacity drive has passed the compatibility test.

Note5
Special handling of disabling write cache on HDD because of the known issue on HDD firmware version SD 15, 17 and 18 of Seagate 1.5TB (ST31500341AS).
Please upgrade your NAS to the firmware version as below
VS-5020 will support 1.5TB HDD on 2.8 version
TS-509 Pro: v2.0.3 Build 1111 or later
TS-409 Series: v2.1.2 Build 1112 or later
TS-109/209 Series: v2.1.2 Build 1114 (for TS-109 Series)/ Build 1113 (for TS-209 Series) or later.

Note6
If you are using two 1.5TB or 2TB hard drives in TS-209, due to an upper limit of the logical volume capacity, you can only have either the Single Disk Volumes(s) or the RAID 1 Disk Volume.

Note7
For improved stability, users are adviced to contact Western Digital after Nov. 15, 2009 for the new firmware upgrade. Please refer to http://files.qnap.com/download/Forum/WD_New_Firmware_Release.pdf

Note8
For improved stability, please update your NAS firmware to v3.1.2 Build1001 or later. There is known performance issue with WD15EADS-00P8B0 and WD10EADS-00P8B0. These two HDDs are not suggested to use with QNAP NAS.