Comment 326 for bug 59695

Some new laptops are shipping with hybrid hard drives that contain non-volatile cache memory (e.g. Sony Vaios with Seagate Momentus drives, 256 MB nvcache). One of the purposes of this technology is to prevent the hard disk spinning up when doing small intermittent writes, which would reduce the severity of cycle count increases on these drives. At the moment the kernel does not support nvcache, although the specification is freely available at t13.org. While flash memory may one day soon supersede spinning disks, in the interim only Vista supports hybrid drive technology. One way to prevent cycling on hybrid drives would be to enable nvcache functionality.
see https://bugs.launchpad.net/bugs/178654