Here is a response I got from Piriform Support on the subject of the OPTIMZE function on SSDs.:
"Defraggler will use a 'zero-filling' technique to optimize SSD's."
Zero-filling an SSD is a trick used to improve write performance. SSD can write data quickly only to a blank (zero-filled) block. But if there are no blank blocks, then it is necessary to erase some blocks before new data can be written. The process of erasing takes a long time. The need to erase blocks decreases performance of an SSD. Therefore, zero-filling applied to an SSD speeds write operations up for a while.
Note that Windows 7/8 and newer versions of iOS and Linux, all support TRIM, which does the same thing, but I'm not sure if it's done on the fly, or as a background task, done when system is idle or whatever. That info seems hard to find. If someone has that info, it would be good to know, same for the Linux and iOS methods. I suspect it is done in the background during idle periods, but I'm not sure. It may run TRIM on the fly as needed when the space is needed, but that would be a most in-efficient way of doing it.
I ran the DF OPTIMIZE on my SSD and noted a message warning that a temporary loss of drive space will occur, and it did. I'm running W7 Pro with an OCZ Vertex III 256GB drive, with 107GB free. It took about 5 minutes to run, and I watched my free space slowly dwindle down to near absolute zero, then quickly return to 107GB free. It seems to be part of the zero fill process to fill first, then mark them all as free at the end. For this reason, I highly recommend closing any and all applications before running this, to prevent anything from possibly needing to write something or need space while the OPTIMIZE is running, the risk is probably very low, but I could see potential for a crash if the drive gets zero filled just as an app tries to write something, and there is no space available. It was a bit unnerving to watch that happen, but all went fine. Just the same, always make sure you have a backup, which everyone should anyway.
After it ran, everything seemed fine, no problems. System performance seems a bit snappier with some tasks, but overall no significant notice of improvement. I will probably run the OPTIMIZE every 90 days or so, just for grins. It certainly didn't hurt.
