If you are considering booting your new Raspberry Pi 4 from a solid state drive (SSD) you might be interested in performance testing carried out by Avram Piltch over at Toms Hardware. Providing insight into what you can expect in the way of performance from a Raspberry Pi SSD setup.
As you might already imagine you will get significantly faster performance and file transfers thanks to the new Raspberry Pi 4 being equipped with USB 3.0 ports. When compared to the Raspberry Pi 2 USB 2.0 ports offering theoretical 480 Mbps / 60 MBps maximum speeds, the new Pi 4 can theoretically provide speeds of up to Gbps / 620 MBps. To compare the speeds even more if you use the microSD card reader on the Raspberry Pi for you can expect transfer speeds of 50 MBps. But how much faster with the performance be if you connected an M.2 NVMe SSD to a USB 3.0 port?
For a full in-depth analysis and more performance charts jump over to the Toms Hardware website via the link below. Which explains that : “Random writes are even more important than random reads because the OS and software (ex: your web browser storing its cache) are always writing small files, so slowness here leads to sluggishness and unresponsiveness. The SSD on the Pi 4 definitely rules the roost here, and even the Pi 3 B+ benefits from solid state storage. But the USB flash drive is a disaster here at 4K, making the microSD cards look good. No wonder I saw lag even when opening the start menu with the USB Flash drive.”
Source: Toms Hardware