Normally, any problems with these units go unnoticed due to their strengths. A SATA drive can be up to ten times faster than a SATA hard drive, not to mention PCIe drives. An important factor that allowed computers to boot up almost instantly or reduce game loading times.
Gaps in data writing
You first need to know a little better about how NAND storage technology is structured internally. What we have inside the NAND units is called pages and these have a size of only 4 KB. Within each block we can find a total of 64 or 128 pagesaccording to the manufacturer’s design.
These blocks are then formed into a set of plans. In turn, a set of planes forms a die, and ultimately a set of these dice will make up the flash memory chip that we see on any SSD. As you can see, the internal structure of these chips is somewhat complex.
We see that this structure is much more complex than any mechanical hard drive on the market. Hard drives simply have plates with “grooves” recorded using special heads. The process of reading and writing in a mechanical unit is much simpler, although slow because it has moving parts.
SSDs have a big problem when it comes to overwriting existing data. The problem is that if we have a file in the block that we want to write, we must first delete that original file and then rewrite the information.
This process leads to another associated problem. As we’ve seen, the smallest unit of information storage is the page, but the smallest unit of erasing an SSD is the block. This means that when we want to update only a small part of the data, all the data in the block must be deleted. The valid data from the previous block is then merged with the new data and finally, everything is written back to an empty block.
Memory Amplification Operation
Let’s say we want to edit a 4 KB file stored on our SSD. Typically, the SSD controller cannot only update these 4 KB stored in a page, it must read the 512 KB (if the block has 128 pages) that the 4 KB page has.
Once read, proceed to delete the 512 KB of information. The next step is to rewrite the original 512 KB, deleting the 4 KB of the original page and now writing the new 4 KB of the new page to a new blank block. That is, it copies the data into a new block and modifies the information we requested.
This process of modifying only 4 KB of data is equivalent to erasing and writing all 512 KB of data. A process that generates us is an amplification of writing.
Impact of this process on an SSD
You probably think it’s not that bad, but this process happens a lot of times on your SSD. Actions such as editing a document or changing the size of an image, among others, force your storage unit to do this.
You should know that SSDs have mechanisms to offer a read and write load which prevents excessive wear in certain areas. In addition, these units have what can be called “reserve blocks” which are additional blocks that will be activated when a block has operating problems due to its use.
The smaller the number of “spare blocks”, the smaller the amount of space for modifying and writing files, and the more scattered the files will be. Paradoxically, this problem leads to greater amplification of writing.
The process of each write operation involves a large number of reads, erases and multiple writes. When the number of spare blocks reaches a critical point, random slowdowns may occur, as well as an increase in the number of unnecessary erases and writes. Therefore, the useful life of our SSD will start to drop.
How to fix write amplification?
There’s not much we users can do. You should keep in mind that although this is an intrinsic element of SSDs, it does not work the same in all of them. If we choose products from reliable manufacturers such as Samsung, Crucial, Kingston, Corsair and many others, this problem is greatly alleviated by special algorithms in the controllers. Additionally, there is the storage cache, which also alleviates this problem.
The only measure we can take is to avoid overloading our SSD. Come on, let’s prevent the bar that Windows displays of our hard drive’s capacity from turning red.
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