I regularly used Piriform's Defraggler to defrag my hdd. Switching to SSD, I thought it was no more necessary, as SSDs do not require defrag.

I used it to make a benchmark, and the program proposed to run a SSD Optimization on my SSD.

Can you explain in what does this consist?

2 Answers

At best it can TRIM the disk. Effectively running through any unallocated space and telling the drive what areas are specifically unallocated and can be reclaimed for use. The blocks that are reclaimed can be pre-emptively erased before they are required for writing and so potentially improve performance.

Trim was introduced soon after SSDs were introduced. Because low-level operation of SSDs differs significantly from hard drives, the typical way in which operating systems handle operations like deletes and formats resulted in unanticipated progressive performance degradation of write operations on SSDs. Trimming enables the SSD to more efficiently handle garbage collection, which would otherwise slow future write operations to the involved blocks

If the blocks are not erased beforehand then you may notice a drop in write speed as they must be erased before being written.

This should already be being done on a regular basis by your operating system, but there should be little harm in issuing a TRIM slightly more regularly. There's little reason to do it more often either than really necessary though, unless you regularly fill up and delete a lot of data on your disk.

Actual defragmentation though is pretty unnecessary and potentially harmful to the lifetime of the drive as it will be actively copying and writing to the disk and wasting cell write cycles.

It seems to just run TRIM.

From their website:

Defraggler and SSDs

What is the TRIM function?

As with a standard HDD, over time, the performance of an SSD will deteriorate with use. This is due to the method in which the SSD reads and writes data.

For example: When you write a file to a new SSD, it will be written directly to the block at full speed. However if you then delete this file, it is not instantly removed. The space it occupies is instead marked by the operating system as “not in use”. When the space is required by the operating system, it will overwrite this space.

However, unlike a standard HDD, it cannot do this in 1 action. It must first erase all the data before it is able to write the new information to the block. When deleting a file on an SSD, a TRIM command is also sent to wipe the marked block clean. This means that the SSD can now write to a completely blank block.

Defraggler is now able to use this TRIM function to optimize your SSD.

What is Zero Fill?

There are occasions when an SSD is not TRIM-capable. In the event of this, Defraggler is able to use an alternative method to help improve the write speed performance of your SSD. This is known as Zero Filling.

The performance of an SSD is based around the time taken to write to a block. This is at its quickest when the block is blank (zero-filled). If there are no blank blocks left, blocks must be erased to provide space for the new data. This slows down the write process. If there is no TRIM function available, the SSD cannot erase the blocks in advanced.