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 150 GB have been written, which is one third of the whole capacity. This means that the Marvell controller uses the whole drive as SLC cache. SLC uses three times as much capacity than writing to TLC. Once the SLC cache is exhausted, speeds drop to around 250 MB/s, but recover fairly quickly after the SLC cache gets flushed to TLC.