Windows 7 gets SSD-friendly

Windows 7 may look little different to Vista on the surface, but there’s a lot of re-engineering taking place under the hood. One of the changes involves making the OS work better with solid state drives. SSDs require a different approach to mechanical hard disks but Vista treats them pretty much the same, which means it can’t take full advantage of the inherent speed benefits of a solid state drive.

The reason? SSDs were but a flight of fancy when Vista was in development. The biggest role that flash memory played on a Vista system was to speed PC performance through use of ‘hybrid’ disk drives or motherboard-resident cache (such as Intel’s Turbo Memory), or by treating a USB flash drive as if were RAM.

Now that’s changed, and solid state drives have replaced hard drives as the storage medium on many notebooks and notebooks. At last week’s WinHEC techfest, Microsoft announced it wanted Windows 7 to make better use of SSDs.

“SSDs are on the path to reach their full potential” says Microsoft senior program manager Frank Shu, who in a conference session on Windows 7 Enhancements for Solid-State Drives outlined how Windows 7 will be more SSD-friendly than Vista or XP.

First up, Windows 7 will seek to “more efficiently” partition the solid state drive so as to minimise unnecessary read-write cycles. The disk defragmentation service will also be disabled when Windows 7 detects installation on an SSD, as defrags are said to shorten the lifespan of a solid state drive without improving its performance.

Defragmentation is intended to boost read times by ensuring that all data blocks in a single files remain together. But flash memory already has a high read rate, so the gains are negligible – but the process of shuffing the data around the SSD gradually wears out the drive due to the need to ‘flash’ each cell with a burst of high voltage.

Shu also says that Windows 7 will come with a new “trim” feature that will cut down on the amount of data to be deleted (to further extend an SSD’s lifespan) and delete garbage data in advance (to speed up the writing of data, which is the activity where SSDs are slowest). Windows 7 will also use particular ATA commands which further improve SSD write speeds.

Microsoft also intends to  launch a certification program for SSDs which give priority to reading data over slower data writes rather than treating both equally and use a native Serial ATA interface rather than Parallel ATA.

However, Windows 7 is unlikely to adopt the newer Non-Volatile Memory Host Controller Interface (NVMHCI) which has been designed specifically for SSDs. Intel created NVMHCI as part of its push into solid state technology and intends it to replace the ATA interface, which was developed for hard disk drives.

“It's too early to say if NVMHCI will make it into Windows 7” says Jeff Price, senior director of Windows product management. “The availability of NVMHCI hardware is still nascent”.

Another SSD-centric focus for Microsoft is ensuring that Windows 7 can fit on the smaller solid state drives of netbooks. While most of today’s SSD-equipped netbooks ship with a maximum 8GB drive, this is expected to double within the coming year. And it’ll need to, because Windows 7 will lay claim to almost half of that space.

At last week’s WinHEC confab, Microsoft senior lead program manager Leon Braginski said that the OS and auxiliary files – ranging from restore files, temp and system log points and disk space reserved for hibernation – will require only 8GB, leaving the remainder free for applications and user data.

“The entire install of Windows 7 will be smaller than Vista,” Braginski said, making 16GB “enough for a good Windows 7 experience.” Braginski declined to comment on rumours that Microsoft would create a special stripped-down ‘netbook edition’ of Windows 7, but confirmed that Microsoft has no plans to craft a different UI for Windows 7 to suit a netbook’s smaller screen.