Ever since Western Digital launched the Raptor series of 10,000rpm hard drives there have been no real speed boosts seen with mechanical hard drives. 7,200rpm is still the fastest speed that normal drives attain, and it seems like this will forever be the standard.
Some companies are experimenting with different takes on mechanical hard drives. Most notable is Seagate, whose Momentus XT drive is a 'Hybrid drive'. This means that Seagate pairs a normal 7,200rpm drive with a small amount of high quality SLC NAND flash. The drive firmware then mirrors the most accessed parts of the hard drive to this flash memory, thus speeding up access to the most used files. What results is faster performance than a normal drive, while costs are kept low thanks to the small amount of flash used.
Where Flash really shines though is in Solid State Drives. These are slowly coming down in price, and while they still cost orders of magnitude more than traditional spinning drives, they have already found a solid niche as low capacity operating system drives. Nowadays a 100GB SSD will set you back around $400, while a 1.5TB 7,200rpm hard drive can be found for $100. A 40GB SSD, which is enough to run Windows from, will set you back about $160.
Once you use a SSD for a boot drive it is hard to go back to spinny media. Windows loads quickly and feels more responsive, and any file access from the drive is tangibly faster than what you would have experienced. The speed of a SSD is largely down to two things, the choice of controller chip used in the drive and the Serial ATA 3Gbps specification.
All the SSD controllers currently on the market support SATA 3Gbps, while newer motherboards come with support for SATA 6Gbps. Until a new generation of controller chips arrive, this will provide an upper limit to the speed of most SSDs. It is a known issue and one that is hard to avoid.
OCZ has avoided the problem by abandoning the SATA connection entirely on its new RevoDrive. Instead it has taken two Sandforce controller chips, MLC NAND flash and a Silicon Image raid controller chip and built a PCI-Express based drive.
PCI-Express provides much more bandwidth than SATA – the x4 link that the RevoDrive uses is capable of transmitting data at 10Gbps – which makes it an ideal platform for high speed storage. This has been known for some time, but until now PCI-Express has been reserved for high end enterprise products. The real brilliance behind OCZ's RevoDrive is that the company has managed to make it affordable, not quite as cheap as a 2.5in SSD but close enough to be viable.
We first encountered the RevoDrive back at Computex, and have been eagerly awaiting it ever since. In the past week we have had a $500 120GB RevoDrive in the PC Authority labs for testing, and it really has blown our minds.
Our first tests of the drive were with HDtach, and it managed to deliver an astonishing 499MB/s result in the burst read tests. We also timed the boot speed on our test system. We used several drives, the Sandforce-based OCZ Vertex LE SSD took 20 seconds to boot, and a 10,000rpm Velociraptor hard drive took 30m seconds. The RevoDrive took a mere 15 seconds.
This is one incredibly exciting development in the world of SSDs. For full benchmarks you will have to wait for our review in next issue, but for now rest assured that the RevoDrive lives up to its big promises.