Solid State Drives (SSDs) might be the newest and fastest form of storage around – but even though their price is coming down, when it comes to cost versus capacity, the good old mechanical drive still holds sway. The new WD7500 Scorpio Black (WD7500BPKT) is the largest capacity drive to date in Western Digital’s Scorpio Black performance range of 2.5in drives. It combines a 750GB capacity with a 7,200rpm spin speed – and it comes with a reasonable price tag, too.
Performance versus capacity
Buying a hard drive used to be a compromise between price and capacity – but with the arrival of SSDs, performance has become another piece of the jigsaw to worry about. If you want out-and-out performance without worrying too much about a large capacity, then an SSD is the way to go.
If, on the other hand, it’s capacity you need – that’s the domain of the mechanical drive. High-capacity SSD devices remain eye-wateringly expensive. For an idea just how expensive, the price of the WD7500 will buy you an SSD with a capacity of just 64GB SSD. For an SSD that matches the WD7500′s 750GB storage space, you’ll be looking to spend at least £1,650 on something like OCZ’s IBIS 720GB drive.
Under the skin
To arrive at its 750GB capacity, the WD7500 packs in two disk platters. Due to the use of the latest Advanced Sector Formatting (ASF) technology, these have an areal density of 520Gb/in². That’s not quite as high as one of its competitors, Toshiba’s MK7559GSXP, which boasts 541Gb/in² per platter – but it’s enough to provide the Western Digital with a capacity of 375GB per platter.
Getting the maximum possible areal density on a disk is the thing that taxes disc engineers probably more than anything else, as it allows more data to pass under the read head on each pass of the disc, which will in turn increase the sequential throughput.
The downside of greater areal density is that the more tightly packed the data, the harder it is for the head to target the information it’s looking for, resulting in slower random access times. To lay claim to its performance disk tag, Western Digital has matched the drive’s 7,200rpm spin speed – a rarity among 2.5in notebook hard disks – with a healthy 16MB cache.
We pitched the WD7500 against one of Toshiba’s 2.5in 750GB drives, the MK7559GSXP. The two share the same capacity and ASF technology, but Toshiba’s the mainstream drive that it is. The WD7500 produced a speed of 248MB/s in HD Tach’s Burst Speed test, whereas the MK7559GSXP could only manage 200MB/s. The WD7500 was faster in the Random Access test too, 15.1ms compared to 17.6ms.
Company: Western Digital