Now that the prices of SSDs have dropped to well below 50 cents per GB, we expect that only few Hardware.Info readers will still want to use a conventional hard drive as their primary storage device. We still can't quite live without them, however, because with prices of around 5 cents per GB, hard drives still remain a much cheaper way of storing large amounts of data.
Hard drives haven't seen all that much innovation during the last few years; manufacturers are primarily focusing on increasing the capacity of their products by increasing the data density of the magnetic disks (the so-called platters) found within the drives. At the time of writing, the largest platters that Western Digital and their subsidiary HGST use for their 3.5″ drives have a capacity of 1200 GB each. Through combining five such platters in a 3.5″ enclosure, they are capable of manufacturing drives with a storage capacity of 6 TB, the second largest drives featured in this round-up. Competitor Toshiba currently uses platters with a maximum capacity of 1000 GB. The platters with the largest capacity can be found in the Seagate Archive HDD 8TB: due to the use of a new technology, Seagate managed to cram 1333 GB on a single platter. More on this later.
For 2.5″ hard drives, the platters with the highest data density currently have a capacity of 500 GB. As such, manufacturers are again forced to combine multiple platters to create drives with higher capacities. The maximum number of platters is limited by the height of the drives. The standard height of 2.5″ drives is 9.5 mm, which is only enough to accommodate two platters. Various modern laptops can only house drives of up to 7 mm in height. Usually, such drives only have a single platter, but Western Digital and Toshiba also managed to create 7 mm models with two platters. Our test also features a 2.5″ drive with a storage capacity of 2 TB, and thus, with four platters. However, with a height of 15 mm, this model isn't exactly suitable for laptops. Instead, it could be used in Mini-ITX computers, 2.5″ NAS devices, and for other such purposes.
Generally speaking, the higher the data density, the better the performance. After all, higher density means that more data will pass by the read and write heads during each revolution. While one can still safely state that hard drives that operate at 7200 revolutions per minute (rpm) will generally outperform 5400 rpm models, certain 5400 rpm models with very high data densities are already awfully close. That said, having a high data density is no longer always an advantage, as certain technologies that increase data density can also have a negative influence on performance...
Special thanks to Dutch web shop Informatique for providing a large amount of hard drives for this test.