Summary: Bought this for back up for my DS214+. It was easy to set up and can be an additional RAID volume or 2 additional single disk volumes. I'm not sure why some are complaining about the plastic housing. I find the plastic units are much quieter than the metal cased units (I also have a DS212j which is white plastic). The plastic cases seem to silence the fan and HD noise much better than metal cases.
A VERY HIGH QUALITY UNIT AT A VERY AFFORDABLE PRICE
HENRY B. ROSE, Amazon
3 June 2014
Summary: I have been marketing upscale home and office server and audio systems. I begin with an 1812+ Synology server and wanted to verify Synology's claim that this unit was a seamless addition. Experimenting with various HDD's, I've settled on Western Digital Red 3TB units as they are the best bang for the buck, so to speak.
Summary: I love all of their products. This allowed me to easily expand a client's DS710+ that had 2x4TB to 4x4TB of storage. Just plugged into the DS710+ with the provided custom eSATA cable and you are good to go. The custom eSATA cable contains thumbscrews that hold the cable SOLIDLY in place. Frankly I've never been happy with "regular" eSATA cables as they can easily be disconnected with the slightest of bumps.
Summary: I have a Synology DS213+, Upgraded from an original ReadyNAS. I underestimated the storage I would need and with just the DS213+ so I purchased the 2Bay Expansion Unit. For hard drives used the WD Red 3TB, which are also in the DS213+. Hook up was easy for power and link cable to the main unit. As noted by some others I want to point out a few things. 1. The unit does not just add the additional space to what you have.
Summary: This expansion unit is not supposed to work with my DS212+ Synology unit according to their web site. Of course, it does. Set the rear switch to have it power up with the NAS as well as power down at the same time. Great convenience. Or leave it powered off when not needed. On my (lower end) NAS it cannot expand an existing volume. I knew this going in and I set up a 2nd volume of 2 x 2TB drives to copy my WAV files to.