The hard disk has been with us for longer than you'd realize. The first examples materialized back in the 1950s, and the IBM Winchester format which we still essentially use today arrived in 1973. Since then, pundits have predicted the hard disk's doom more than once. With the rise of Flash memory in mobile devices, which have been pushing down unit prices, it is expected that solid state disks (SSDs) will take over from the mechanical variety sooner or later. But while there are no signs of this happening just yet, there is new technology bubbling under which could see Flash memory taking a greater role in PC storage.



Drive Time

The spectre haunting HD technology is the ‘superparamagnetic effect'. This supposedly sets a limit on how small the magnetic grains on a hard disk can be. Below a certain grain size, the temperature raises enough to reverse the magnetic polarity of grains. This makes the hard disk unreliable. For the time being, the superparamagnetic effect is being held at bay by new developments like perpendicular recording which allows the use of larger grains by stacking them on their ends perpendicular to the hard disk surface. With traditional recording, grains run parallel to the disk surface, so take up more room. In the long run, though, perpendicular recording will only delay the hard disk's execution.

Flash memory also requires much less power than a mechanical disk. Additionally, Flash offers much lower access times than those of a hard disk. As a result, Flash hard disks offer boot up times 25 – 50% quicker than conventional hard disks. On the down side, Flash memory is still only available in fairly meager capacities, and those are hideously expensive.

Mix and Match

SSDs have their good and bad side compared to HDDs. This has led to a new idea; why not use both at the same time. Samsung was the first to publicize the concept, and has been talking about its Hybrid Hard Disk (HHD) for the last 2 years. This bolts 128MB of Samsung's OneNAND Flash memory onto a regular hard disk. The Flash is used as a buffer, storing write tasks until it is full. Only then is data written to HHD. This way, during times of light usage, the hard disk can remain idle or even in sleep mode for much longer. Samsung claims this reduces power consumption by an average of 9%.

Seagate's Momentus 5400 PSD takes a similar approach, but uses twice as much Flash (256MB). Seagate maintains the greater capacity reduces power consumption by as much as half.

Since Flash maintains its data without power, it's an ideal place to store part of the hibernation file. Seagate argues this reduces recovery time from hibernation by 20%. Using a flash buffer can also extend the life of your hard disk, which is usually measured in terms of the average number of hours it can be in use before failure occurs.

Despite Samsung being the first to publicize the HHD, it was developed with Microsoft. In fact, two technologies within Windows Vista will make use of it. ReadyDrive is what Microsoft calls support for HDs within Windows Vista and a driver will be needed to manage the process. But Microsoft has a more surprising take on the hybrid idea, too. In recognition of the ubiquity of Flash RAM thumbdrives, Windows Vista will also contain ReadyBoost, which anyone can use. Instead of having the Flash cache built into the hard disk, ReadyBoost can use a thumbdrive instead.

Perhaps the most viable version of the hybrid idea is the one Intel is currently calling Robson. Instead of relying on the hard disk or third party add on for the Flash memory, Robson places it directly on the motherboard, connected to the Southbridge via PCI Express. That way, any disk can be used, and you don't have to worry about compatibility issues.

The benefit of ReadyDrive is to power consumption, so it's aimed primarily at portable computers. But with 4GB already being launched for ReadyBoost, the hybrid idea is starting to have clear implications for the desktop PC as well. So perhaps the SSD will take over from the HDD as has been predicted for so long – just in a slightly more surreptitious manner than we originally expected.