I am excited to see that they have USB boot on the pi 4 now, so I decided to try booting on an old ssd I had. I used a really old 80GB intel ssd (2009?) in a usb 3 enclosure on my Pi4 4GB. I have other newer ssds but they are all being used for various things. I was already using one of the faster micro SD cards you could buy with the Sandisk Extreme Plus 32GB A1, so this difference is probably more on the worse case and if you have a slower SD card and faster SSD, the improvements will be far better I imagine. I timed it from when I hit the button for power on the unit until the icons loaded on VNC desktop. https://speedtest.vet/ https://vidmate.bid/ I do have a full time vpn on my pi that has to connect before the desktop shows, so that adds a few seconds. I also included the systems-analyze numbers reported by Linux to make it more precise than me clicking start on a stopwatch.
I ran it a few times and the results were pretty consistent. I wish I had one of my fast SSDs available to test with, and I may try again. I think the pi 4 usb speeds cap out at around 350MBps, so there may not be a huge difference.
Pi4 4GB @2.0GHz
32GB Sandisk Extreme Plus A1 V30
80GB Intel X25m in cheap rosewill usb 3.0 enclosure
Total hand calculated time:
With MicroSD: 44.2 seconds to desktop.
With SSD: 38.4 seconds
System reported time:
MicroSD: 1.699s (kernel) + 26.729s (userspace)
SSD: 1.074s (kernel) + 21.935s (userspace)
I am curious to see how it is working for everyone else that tried it. It was super easy to get it up and running as I just cloned my MicroSD card to my SSD. Great time waster project.