This is the first 8TB hard disk drive we've received at TechRadar and the biggest external (single-drive) hard disk currently on the market. This particular model ? the Seagate Backup Plus ? was announced earlier this year but uses an enterprise-grade drive which was unveiled back in August 2014. You could probably cram about 1500 DVDs in 8TB or the content of 160 Blu-ray discs, or the equivalent of almost six million 3.5-inch, 1.44MB floppy disks (remember those?).Seagate's mammoth drive, otherwise known as the STDT8000200 in the UK and STDT8000100 in the US, is so new that it hasn't appeared on the company's own website yet. It sells for around the £250 mark (around $365, AU$485).SMR magicSo how exactly did we get there? This storage capacity was achieved by making use of a new technology called SMR (Shingled Magnetic Recording) which allows the cramming of more bits on a given surface by using a similar technique to what roofers do with roof tiles.Drives that use SMR have one flaw ? they do not perform well when it comes to sustained, random writes. They do however excel when it comes to sustained read speeds and burst write speeds.