Seagate today launched its Momentus XT drives, with performance it claims is close to an SSD drive, but at a fraction of the cost.
The innards of the hybrid drive do not actually look like this artist's representation of SSD storage melded with a mechanical hard drive -- but the picture does demonstrate the point.
The trick with these drives is that they have 4GB of flash memory to provide fast access to your most commonly accessed data – while the rest of your data goes on the conventional 500GB of spinning hard disk storage (which is no slouch, either, at 7200RPM.)
The 4GB flash memory uses the faster single level cell (SLC) technology, where only one bit of data is stored in each flash memory cell, rather than the slower but cheaper multi-level cell (MLC) technology used in most SSDs.
But these are not your grandfather's hybrid hard drives (to use a horribly stretched metaphor), said Seagate Australia senior field engineer Sam Zavaglia.
The first batch of hybrid hard drives in 2006 – which proved to be a big flop in the market -- "relied on special support from Windows Vista or Windows 7 and you needed a BIOS that supported it, and even then they really only helped with bootup speed," Zavaglia said.
"The new Momentus XT drives are completely independent of software support and will work in any PC," he said.
They're file system and operating system agnostic – they cache portions of data from the hard disk based on what is accessed the most frequently. Seagate has developed a proprietary algorithm called "Adaptive Memory" to do this, and once files were in the 4GB cache they can be rapidly retrieved.
As a result, when users first use the drive, they won't notice much speed benefit over a traditional 7200rpm hard drive, he said, because all the files would be loading from the mechanical hard drive platter. After a couple of uses of a file, though, it would be pushed into the 4GB flash cache.