pSLC Cache / Write Intensive Usage

When copying games from your Steam Library, or other very large files (>10 GB), you may notice that write speeds on your SSD start at full speed, before dropping considerably. The underlying reason is that modern drives have small, fast caches, that soak up write bursts to improve performance. In the fairly uncommon scenario of writing data that's too big to fit into these caches, the drive will have to write data directly to flash, and it will probably juggle some out of its write cache at the same time, which can result in a significant loss of write speed. Newer TLC drives use part of their capacity in SLC mode for increased performance. This test can reveal the size of that pseudo-SLC cache.

Testing on this page looks at exactly that scenario. We write a sequential stream of 1 MB blocks to the drive in a single thread, like a typical file-copy operation would do, and measure write speeds twice a second. The drive is fully erased before testing to ensure any caches are emptied. Please note that this test writes a lot of data in a very short time, something most consumers will never do.


Write speed starts out at around 4.7 GB/s, which is very impressive for single-threaded write speeds. These speeds are sustained until 48 GB have been written—a really tiny SLC cache, especially for a modern SSD in 2024. This cache size is among the smallest I've seen in many years, no idea why Corsair picked such a small setting. Once the SLC cache is full, speeds drop to 1.5 GB/s, which is a very decent result for a midrange drive. Filling the whole capacity completes at 1411 MB/s on average, a good result that's better than most competing drives, but similar to what the E21T offered.