With Windows 8, there is an option to "optimize" a drive. This looks similar to the Defragment option of previous versions of Windows:
I have an SSD and I know that SSDs shouldn't be defragmented. However, Windows 8 recognizes that the drive is an SSD, and still says it needs optimization. What exactly does the "Optimize" option do in Windows 8? Is it safe for SSDs?
Best Answer
What this does is run the Trim command on the drive (if it supports it). It does not actually defrag the drive, as is the case with a traditional rotating drive. It is probably a good idea to execute Trim to wipe blocks which are no longer in use.
The Windows Assessment Tool (winsat) is what initially determines whether or not the drive is an SSD and switches the behavior of Disk Optimizer. Under Windows 8, winsat runs under the Microsoft\Windows\Maintenance schedule in the Task Scheduler. This is the same tool (winsat) that would disable defragmentation of SSDs on Windows 7.
Just to re-iterate the point and drive it home: Do not think of Disk Optimizer under Windows 8 strictly as Defrag; it is now a general purpose tool that performs the appropriate disk optimization task based on the type of disk which is attached. The identification of disk type is based on winsat.
Official response to a similar question at answers.microsoft.com