Best Hard Drive 2015 - The top HDDs for speed and price

Few things are as vital to a PC or laptop as its internal disk drive. Not having enough storage is immensely frustrating, as you have to uninstall programs to make room for the latest game, or shuffle your files around to external storage to download a rented film. Also, slow hard disks can make your computer feel sluggish, as the operating system and applications take ages to load.

Both these problems can be solved with a drive upgrade. Mechanical hard disks are frankly astounding value, proving thousands of gigabytes of storage for less than 3p a gigabyte, though they're not as quick as SSDs admittedly. Hybrid drives try to bring you the best of both worlds, combining the speed of an SSD with the capacity of a traditional magnetic disk.

If you're fitting a disk to a desktop PC, you don’t necessarily have to choose between a hard disk and SSD, as you could have a fast SSD as your system disk, and store your files and documents on the slower hard disk. If you have a laptop, you usually have to make do with one drive only, so either have to decide whether speed is more important or capacity - unless you fit a hybrid drive. Bear in mind that some laptops don’t have standard hard disk bays or don't let you upgrade the disk at all, so check before you buy.

Seagate Laptop SSHD - Seagate’s Laptop SSHD has plenty of form factors to support different sized laptops

£67 inc VAT (1TB) From www.scan.co.uk

Seagate’s Laptop SSHD hybrid drive combines a hard disk with 8GB of flash memory for frequently-accessed files, to help bring the storage space of a mechanical disk with some of the speed of an SSD to laptops. The hybrid drives are available in different form factors to support a multitude of systems. There's a standard 7mm size (ST500LM000) that will support most laptops, 9.5mm (ST1000LM014) for large desktop replacement models and a super-slim 5mm drive (ST500LX012) for Ultrabooks, so it’s important you buy the right drive for your system.

The 7mm and 5mm drives are only available in 500GB capacities, while the thicker 9.5mm drive is available in a generous 1TB; this is the model Seagate sent us to review. This works out at around 6p per GB, making the drive good value. The 1TB drive has four heads and two platters, which explains the additional thickness. The drive operates at 5,400RPM, which is standard for most laptop disks. All the Laptop SSHD capacities include a cache of 8GB of MLC NAND flash memory.

The SSHD’s controller uses an algorithm to learn which files you use most frequently. It then moves these files to the NAND flash for faster access. This process doesn’t require any drivers, so it should work in Mac and Linux laptops, as well as on Windows.

Overall performance in our benchmarks was excellent. The drive could write large files at 132.1MB/s and read them at 133.9MB/s; the large file write speed in particular is one of the best we’ve seen from a laptop disk. Small-file transfer speeds were also very good, with 82.7MB/s write and a huge 92.7MB/s read, for an average of 87.7MB/s - the best score we've seen from any 2.5in or 3.5in disk.

Due to the way the cache works, we were expecting subsequent benchmark runs to show even faster speeds, but this wasn't the case; even after four or five runs we saw no improvement over the first time we ran our file transfer benchmarks.

The drive's hybrid technology also came into its own when booting into Windows. The first time we measured it, using the Bootracer utility from www.greatis.com/bootracer, the Laptop SSHD booted into Windows in 50.7s. The second time this dropped to 44s, and once we had restarted six times the cache had managed to reduce the boot time to just 28s.

It may be more expensive than other laptop hard disks, such as the Western Digital Green Mobile, but the fast Seagate Laptop SSHD is a solid upgrade if your laptop’s existing storage is a slow mechanical hard disk. Hybrid drives have always made a lot more sense in laptops where you’re limited to one storage disk, need plenty of capacity and are not looking to spend considerably more on a high-capacity SSD. With the added benefit of the faster boot times and general overall responsiveness, the Seagate Laptop SSHD is a fine upgrade choice.  

Western Digital Black2 Dual Drive - The Western Digital Black2 is a clever combination of a hard disk and SSD all in a single 2.5in form factor

£160 inc VAT (1TB + 120GB SSD) From www.ebuyer.com

At first glance, the Western Digital Black2 Dual Drive looks like a standard 2.5in hard disk. However, it’s actually two disks in one, with both a 1TB hard disk and 120GB SSD in the same shell. Unlike some other hybrid drives, the Black² doesn’t use the SSD as a cache; it's just two drives in a case with one SATA3 interface. The idea is that you install Windows and your programs on the fast SSD, and save the larger, slower drive for all your documents and media files. It’s for this reason Western Digital labels the Black2 as a “dual drive” rather than a hybrid drive.

Conveniently, the Black2 comes with a couple of extras to help you install the drive in your computer. A USB3-to-SATA adaptor and a downloadable edition of Acronis True Image that only works with the Black2 can be used to clone your PC’s existing Windows installation to the SSD. This is a generous pack which will make upgrading a PC or laptop much easier. At 9.5mm, the drive is deeper than most SSDs or laptop hard disks, so if you planning on fitting it in a laptop check your drive bay is big enough.

You don’t need Acronis True Image if you simply reinstall Windows from scratch, but the software driver is essential, as without it only the 120GB SSD part of the Black2 will be visible to Windows. The driver is compatible with Windows 8.1 and Windows versions as old as XP. The drivers are included on a small USB flash drive.

Initially the Black2 launched without driver support for Mac OSX but the necessary software has since been released. You’ll need to update the Black2’s firmware (available from support.wdc.com) to make it work. The entire process is reasonably complicated on a Mac, and setting the drive up for Windows use is certainly simpler.

The Black2’s SSD uses 20nm NAND flash and a JMicron JMF667H controller. The 1TB hard disk has a spindle speed of 5,400RPM and 64MB of cache. As the drives are completely separate, we ran each through our file transfer benchmarks. In our large files test, the 120GB SSD wrote files at 216.2MB/s and read them at 394.9MB/s, for an overall 305.6MB/s. These are very slow speeds for a modern SSD. Small-file performance was also quite average at 93.3MB/s write and 79.2MB/s read. The 1TB hard disk had more impressive performance for a mechanical disk, with a large file read speed of 196.6MB/s and write of 112.3MB/s, which is great for a 2.5in hard disk, but a small-file write speed of 37.9MB/s is very poor. If you're using your disk to mainly store media files, however, this shouldn't be a problem; small-file performance is more important for program and operating system loading.

Since it originally launched, the price of the Black2 has dropped to the point where it costs around £0.14/GB with the capacities of both drives combined, which isn’t cheap. However, if you want the speed of an SSD for your software and operating system, 120GB should be just enough space. You’re then left with a generous 1TB for your media, making the Black2 a good upgrade for a laptop’s storage capacity. You’ll just need to make sure its 9.5mm height will fit in your computer.

Western Digital Green - Great performance for a budget price makes the Western Digital Green hard disk range a Best Buy

£40 inc VAT (500GB), £43 inc VAT (1TB), £64 inc VAT (2TB), £82 inc VAT (3TB), £118 inc VAT (4TB) From www.scan.co.uk

Western Digital’s Green series of desktop 3.5in hard disks has a great combination of low price and impressive performance. It’s difficult to judge exactly what makes the drives perform so well, as Western Digital is secretive about some of the disks' specifications. Rather than list a spindle speed in RPM (revolutions per minute), Western Digital describes its Green disks as using “Intellipower”. According to the company, this is a set of algorithms designed to manage spin speed, transfer rate and caching, in order to deliver power savings and improved performance.

Similarly, there’s no official seek speed rating. Instead the Green range uses Western Digital’s “IntelliSeek” technology. The company claims this provides more accurate control of the hard disk actuator’s movement so that the head reaches the correct hard disk sector just in it time to read or write the next piece of information, reducing power use and vibration.

The Western Digital Green range is available in 500GB, 1TB, 2TB, 3TB and 4TB capacities, so there are plenty of options. The cost per GB for the larger capacities is a very reasonable 3p per GB for 4TB and 2TB and 4p per GB for 1TB, making them a close rival to the Seagate Desktop range in terms of price. The 500GB drive is only £3 less than the 1TB model, so isn't really worth buying.  

All the drives have 64MB of cache and a standard SATA3 connection. Like its predecessor, the Caviar Green range, the Green uses Western Digital's Advanced Format technology, which apparently uses smaller disk sectors to increase the available amount of storage space.

We tested the 4TB and 1TB models and both performed remarkably well considering their low price. The 4TB managed a read speed of 256.9MB/s and a write speed of 195.6MB/s in our large-file test. The 1TB model performed similarly, managing 255MB/s and 201.1MB/s respectively. These large file scores are above average for mechanical hard disks.

In the small files test the 1TB model wrote files at a strong 85MB/s, but the 4TB drive managed a huge 92MB/s, which is the best speed we’ve seen in this test from such a large drive. The 4TB drive could read small files at 73.2MB/s, which again was quicker than the 1TB disk's 65.3MB/s. Considering the drives' low prices, we’re seriously impressed with their performance.

The Western Digital Green range contains some very impressive hard disks. If you’re looking for a secondary drive for your media, the higher-capacity drives provide a great price per GB, and the disks are quick enough to use as a large system disk, too. If you're going to be working with lots of large files, such as when editing video, you should consider the Western Digital Black range with its superb large-file performance, but for most people the Western Digital Green series is the Best Buy.

TRANSFER SPEED GRAPHS 

To test the read and write speeds of each disk drive, we use a script that copies files to and from the drive and measures the time taken. We copy the files to the disk from memory rather than from another disk drive, because RAM is faster than any hard disk or SSD so won’t act as the limiting factor in the tests. In our large-file tests, we copy a 100MB file to and from each disk 100 times to see how fast a drive is when dealing with big files such as video clips. We repeat this test using a selection of smaller files totalling 100MB, to see how well a drive copes with the many smaller files needed when loading an operating system or application. 

LARGE FILE TEST - READ/WRITE AVERAGE in MB/S

SMALL FILE TEST - READ/WRITE AVERAGE in MB/S