Warning!

If you schedule a boot-time disk check, disabling "No GUI boot" will prevent Windows from displaying its progress. You will see nothing but a blank screen, as CHKDSK scans the SSD for errors.

To view the progress and any error message that may appear, you have to disable "No GUI boot" before you restart Windows to let it scan the SSD.

Tech Explainer

The flash memory cells in SSDs are grouped into pages that are typically 4 KB in size, and data is read or written in pages. Writing data to the SSD is very fast, as long as there are empty pages to use. But once it runs out of empty pages, it will have to start clearing used pages because flash memory pages can only be written to if they are empty. If they contain even a single bit of data, they must first be erased before they can be written to.

Unfortunately, the SSD cannot just erase a single page of flash memory if it wants to write to one page. When it comes to erasing flash memory, the SSD has to erase them in large blocks of pages, usually 128 pages or 512 KB at one go. Even if it's to write a single bit of data to a used block, the SSD has to :

• read the entire content of that block,
• erase the whole block,
• modify the content, and then
• write it all back to the block.

This is known as the read-erase-modify-write cycle. As you can tell - it's not only a very time-consuming process, it also increases the wear and tear on the flash memory cells. That's why it is of great importance to reduce them, and this is where the Trim command comes in.

Modern file systems use a trick to greatly improve performance. Whenever a file gets deleted, the file system does not command the drive to overwrite the affected sectors with a series of 0s or 1s or random bits. Instead, it just flags those sectors as "free space" or "not in use" - an instantaneous process. The drive itself isn't aware that a file has just been deleted.

This is perfectly fine for hard disk drives because overwriting the used sectors that the file system flagged as "free space" with new data is no different from writing into empty sectors. However, this isn't the case with solid state drives, because as we pointed out above, it cannot write to used pages - they must be erased before they can be written to.

If the SSD is not aware of any file deletion, it would retain the data instead of marking those pages as dirty so that they can be cleared in the background. When the file system actually commands the SSD to overwrite those pages, the SSD will have to initiate a read-erase-modify-write cycle because they still contain data. In fact, as far as the SSD is concerned, they contain valid data and it is merely "modifying" the contents. This greatly reduces the performance of the SSD and amplifies the amount of wear and tear on the flash memory.

The Trim command allows the operating system to notify the SSD whenever files get deleted so that the SSD controller can mark, combine and queue the affected pages to be opportunistically cleared during idle periods. This will increase the chance that when the file system requests to write data to a previously used page, it will have been erased in the background and ready to be written to. Of course, the SSD itself must support the Trim command.