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See here on the sequential steady state write performance of Kingston UV400.

Therefore it's likely that the Kingston drive filled up its SLC cache quickly, then dropped back to writing to its 2D TLC, which is in fact not much quicker than HDDs. But the Kingston drive does seem to use this strategy. WD drive seems to be clear, since its 3D TLC does not rely on SLC mode cache for burst speed. However, as soon as the cache is saturated, the drive will revert back to a much slower storage medium. This is usually fine, because most day-to-day use does not involve transferring large files. Lower-end drives often reach this speed momentarily using some cache strategy. Simply put, just because the drive advertises 500MB/s, does not mean that you will always reach 500MB/s.

I suspected that the slowdown might be due to SLC cache saturation, and it seems very likely to be the case after a bit of research. The WD SSD is about 25% full, and the Kingston one is just over 5% full.

These are just about new SSDs the WD one is around a year old, whilst the Kingston one is just over two years old. I have tried just about every solution I came across, like Enabling and diabling AHCI, enabling and disabling TRIM, updating BIOS, using RamCache II to allocate more than 20GB of RAM to both SSD, but still no improvement at all. mp4 file of about 12GBs, still same results. I have tested with a folder of multiple files of about 8GBs, and a single large. These are supposedly to have 550MB/s read and 500-525MB/s write.Īt first, when the transfer is initialised, the numbers skyrockets, and they keep on going up till they hit 82-84%, and then they plummet to between 2-14MB/s (keep in mind that this is between the two SSDs). I have two different type of SSDs: The one I have installed Windows on is a Western Digital Blue 3D NAND SSD 250GB (WDC WDS250G2B0A-00SM50), and the other one is a Kingston SSDNow UV400 480GB (Kingston SUV400S37/480G). This usually occurs when the file I'm transferring in-between them is about 84% complete. I am running into an issue where both my SSDs drop to about 1-2% of their write speed.