How to Boot Raspberry Pi 4 / 400 from USB You can also use a standard USB flash drive, though we found the performance worse than a microSD card on many tasks. In our real-life tests of a Raspberry Pi 4 with SSD last year we got impressive performance with sequential transfer rates as high as 140 MB / 208 MBps for reading and writing. Using an external SSD as your main storage drive could speed things up significantly and, with a few commands and a simple firmware update, you can do just that. In real-life, even the best microSD cards for Raspberry Pi get no faster than about 38 MBps in sequential writes. By default, Raspberry Pi boots up and stores all of its programs on a microSD memory card, which has a maximum theoretical bandwidth of 50 MBps on the Raspberry Pi 4 and just 25 MBps on prior models.
