How Windows 7 will, and won't, work better with SSDs
- — 10 November, 2008 09:13
Defragging disks speed ups the reading of data from conventional hard drives by moving similar data together. But flash-based SSDs are already fast at reading data. Rather, SSDs are slow at writing data. Moreover, the process of erasing and moving data requires "flashing" the memory cells with high voltage. That gradually wears out the SSD.
Defragmentation thus shortens an SSD's lifespan without improving performance, Shu said.
Second, Windows 7's new "trim" feature will improve performance three ways. It will: Reduce the amount of data to be deleted, which improves the SSD's lifespan; delete garbage data in advance, which speeds up writing of data; and maximize the amount of unused data, which helps even out the wear and tear on the SSD, Shu said.
Third, Windows 7 will partition the SSD more efficiently to cut down on unnecessary read-write cycles, Shu said. This requires Windows 7 to be installed fresh and not upgraded from XP, he said, since the latter OS formats SSDs in an inefficient way.
Finally, Microsoft plans to create a certification program for SSDs. To win the software maker's logo of approval, SSDs must identify themselves to Windows 7 properly, prioritize data reads over slower data writes, comply with the Serial ATA (SATA) drive interface for faster connections, and more, Shu said.
On the other hand, Microsoft is not taking more radical steps. For instance, it's not trying any tricks to decrease the number of times data is written, such as using RAM to cache data, Shu said.
Writing data to flash memory, especially small amounts of it, takes 100 times longer than reading it, according to SanDisk.
SanDisk's Barnetson agrees that Microsoft is limited by what it can do in this vein.
"The challenge is that it's not just Windows, it's all of the applications constantly issuing commands to the SSD," he said. Software vendors "aren't going to change, that's the reality of it."
Moreover, Microsoft appears unlikely to have Windows 7 adopt a new disk interface technology written specifically to boost the speed and longevity of SSDs. It's called Non-Volatile Memory Host Controller Interface. Developed by Intel, NVMHCI would replace the ATA interface that was developed originally for hard disk drives (though, out of necessity, also used by SSDs today).