I'd realised that SDD's speed to move or copy folder is too slow (SDD M.2), I installed a software to see the spped that it could have, and ins't the same when for example I moving a folder or coping it. See the picture, What's happening here?
In addition, the screenshots had taken without more process os writing or reading, my computer only was moving that folder.
For writing nearly 500,000 files totalling 1.5GB, yes, this is probably normal.
SSDs are fast, but at an average file size of approximately 3kB you are hitting the 4kread/write thresholds:
1 x 4k read to read the data
1 x 4k write to write the data
possibly a couple of 4k reads to find the file location on disk (filesytem overhead)
possibly a handful of 4k reads/writes to find a spare block in disk, to update the file table, directory file table and so on
So you are talking about reading/writing about 10-20 4k blocks just to copy one 3kB file. This is assuming that buffering is largely irrelevant and can only get you so far.
Your Crystal benchmark shows your 4K random speeds as 300-400MB/s, divide that by 10 and you get maybe 30MB/s, divide by 20 and you see 15MB/s.
So to me it seems about right.
If you are being generous and saying that maybe buffering is doing all it can you still have at least 2 to 4 4K reads, and are probably hitting the single threaded 4K random read/write speeds of 48MB/s read / 100MB/s write. A small group of those read/writes interspersed would achieve maybe 15-25Mb/s, which you are seeing.
Using a program such as 7zip to compress all your files into a single monolithic file may allow you to group all the reads into one stage (during compression) and writes into another stage (decompression). Moving a single large file around would also be faster and more efficient than several hundred thousand small files.
Does your computer (hardware) have a SATA 3 interface/bus? If it is older it might only have a SATA 2 or SATA 1. SATA 3 interface gives max theoretical speed of 6 Gb/s, SATA 2 with half that of 3 Gb/s.
Newer SSDs cannot achieve their maximum performance unless you have a SATA 3.
