Random IO

Random read/write performance matters if you copy a lot of small files or use the drive as storage for games/applications that are directly started off the drive.

Sequential IO

Sequential performance is relevant when you copy large files—videos, for example.

Sustained Write Speeds

Sequential write speeds start out high and remain constant until around 55 GB have been written, and drop just a little bit, to 800 MB/s, which are sustained until 150 GB have been written. At 150 GB written, transfer rates drop again, to 600 MB/s—still faster than any SATA SSD. Rates go up and down again intermittently, as the pseudo SLC cache is flushed to TLC in the background. Just like with all pSLC mechanism, rates recover fairly quickly when writes stop and the SLC cache gets flushed to TLC.