Specifications

A dual core Atom CPU is the brain of the NAS, which should be sufficient enough. The available memory is one GB and can be easily upgraded to two or three GBs. Regarding hot-swap, up to six can be installed into this NAS, something that most likely will empty your wallet since the prices of HDDs still remain high. Also before you purchase the HDDs you should better take a look at QNAP's HDD compatibility list, because some disks are not compatible with the RAID levels that the TS-669 Pro supports, or simply cause a lot of trouble. Moreover you can search a little further in the official QNAP forum for opinions of other users who already bought the drives you are planning to get.

Jumping to the network part of the TS-669 Pro, we can see from the table above that it is equipped with two Gigabit Ethernet ports, which support LACP (Link Aggregation Control Protocol). However in order to take advantage of LACP's increased speeds you should connect the NAS to a switch that is also compatible with port trunking, otherwise you won't see any improvements in network transfer speeds. The same applies to Jumbo frames, and in addition you should configure the MTU value of your clients accordingly to fully exploit them.

This NAS is equipped with two USB 3.0 ports which greatly enhance its usability, but unfortunately both of them are located on its rear side. In our opinion at least one USB 3.0 port should be installed on the front, for easier access.

The dimensions of the NAS are not compact, that's for sure, simply because six 3.5" drive bays need lots of space. However you can't call it large either since it has about the same size as an SFF case. Despite the limited space, QNAP managed to squeeze a small PSU in there which can deliver up to 250W, more than enough power for the needs of the TS-669 Pro.

Finally the warranty is set to only two years, a short period in to our opinion, while the price looks highly intimidating at over $1000. However we should not forget that this NAS is not intended for home use but mainly for business environments where reliability and performance come first and cost follows (closely).