I'm going to advise against any such items as Western Digital "MyBooks" and the ilk.
The reason for this is that they typically use two smaller (cheaper) hard drives to get the advertised capacity. The way they do this is with proprietary software - usually Linux based - that arranges the two or more disks into a JBOD (Just a Big Old Drive). They do this using RAID 0 config which means they "stripe" the data - alternating tracks between the two drives. If one drive develops problems you've just lost everything as even the data recovery people will struggle with it. Ask me how I know this. In my case Western Digital compounded the issue by keeping the software on some hidden sectors on one of the drives.
So now I do two things:
1 - a network RAID box to store all working materials (I use DROBO)
2 - a
USB 3.0 SATA dock that accepts 2.5 or 3.5 hard drives. I use this to archive data to a cheap hard drive which gets filed and put away.
You can get a 3.0 cradle for around $30 and a
2TB hard drive for less than $80.
The external hard drive solution works really well as you can put stickers on the end and use those to lookup what's on them.
I would also mention that I periodically load the drive into the dock and do a disk check which seems to help keep the data intact.