IFA 2014 is currently underway in San Francisco, with HGST showing off its newest member in its HelioSeal family, the new Enterprise-class SMR-based 10TB HDD. Yes, you read that right - ten terabytes of storage in a single drive.
HGST achieved this insane level of storage by using its Helium-filled HelioSeal technology mixed with Shingled Magnetic Recording (SMR), but it comes at a price. SMR writes to the disk in a way where its mainly a sequential write/random access read storage device. The tracks inside of the 10TB HDD are slightly overlapped as they're being written to the disk.
Thanks to this method, we have a massively increased density up to 10TB, but writing to the middle of the disk isn't possible without overwriting two shingled tracks simultaneously. PC Perspective explains this as "CD-RW writing, but for hard disks". These new drives will be a better buy than tape-based archiving methods, especially with storage now hitting 10TB per drive.