Do ssds actually still have slc? Isn't it just part of the tlc made to act like slc... or something like that?
SLC Cache is stored in TLC NAND Flash, so if it is not erased purposely, the data can be saved continuously and will not disappear due to power off.
Every NAND package has SLC cache build-in. How big this cache is depends on the price of your SSD.
The SLC cache typically comes in two distinct parts: a static SLC cache and a dynamic pseudo-SLC cache. The static cache is generally tiny,
less than 10GB even on large 2TB drives. The static cache is always available, even when the drive is almost full.
Are DRAM-less SSD worth it?
It depends.
You see, DRAM-less SSDs have a poor reputation in the PC community because their performance can be poor in certain situations. This is because while solid-state storage is fast, there can still be significant latency for information retrieval if the controller does not know where the information is.
Think about it like this (this is grossly oversimplified but works well enough as an analogy):
If you are looking for a book in a library, knowing only its title (the shelves are organized by author name or some other piece of information you don’t know), the slow way to look for the book would just be to look through the books one by one and see which one matches the title you are looking for. This could take a while.
However, a much faster way to find the book would involve asking the librarian to search through his system to find the author of the book you are looking for, and then going straight to the shelf for books with that author’s name.
In this example, the catalog that a librarian keeps in his computer is quite similar to the DRAM on a conventional SSD. It allows the SSD controller to locate very very quickly the location of the information being requested. NAND flash, which is the type of actual storage chip type used on SSDs, is fast but still much slower than DRAM, meaning that a similar “catalog” stored on NAND flash would not operate as quickly.
This means that initially when DRAM-less SSDs came out, their performance hardly lived up to the SSD name. In fact, in some situations, they can even be slower than modern spinning-disk hard drives, which usually half a similar cache to the DRAM chip on an SSD nowadays (albeit smaller to cut down on price). Thus, DRAM-less SSDs were despised by the PC building community.
So why did I answer the question with “it depends”?
That’s because in the time between the initial development of DRAM-less SSDs and current-day, new developments have allowed DRAM-less SSDs to operate with nearly as low latency of traditional, DRAM SSDs.
This development is called host-memory buffer, or HMB. It isn’t magical, nor is it really a revolutionary discovery in computing, but rather, SSD manufacturers simply made the controller on their DRAM-less SSDs ask the CPU (the “host”) for some of its DRAM. This basically means that instead of having a DRAM chip on the SSD itself, the SSD uses some of the system memory to achieve the same results, allowing for similarly fast operations as a traditional DRAM SSD.
Just like an Intel Celeron CPU.
