TechTool Pro will work with Solid State Drives (SSDs). However, because of the differences in how SSDs work contrasting with traditional hard drives, we do not recommend using Volume Optimization.
The principal functional difference between conventional hard drives and SSDs is their method for writing data. In order to write new data to a block on an SSD, the data already present must be deleted first – this slows writing data to sectors of the drive that have old data that has not yet been written over. SSDs that ship with Macs have TRIM support in which the OS ’empties’ erased data so that future writes to those sectors are most efficient. Further, each sector of an SSD has a finite number of times that it can be written to. The most efficient way to write to an SSD, then, is to write to ’empty’ sectors, and to write to each sector an equivalent number of times. Therefore, functions which write to the Disk repeatedly, such as Volume Optimization, are problematic; they essentially force the drive to do the work of erasing and then writing over and over again, shortening the life of the drive. Volume Optimization was beneficial for conventional hard drives because the drive heads would not have to travel as far, making reading and writing data more efficient. On SSDs there are no drive heads, and data is written to all sectors at the same speed regardless of physical location.