OK time to get this Raspbery Pi 400 to boot from a Corsair Voyager GTX memory stick!
`hdparm -t` on the current Samsung PRO U1 microSD card:
/dev/mmcblk0p2:
Timing buffered disk reads: 116 MB in 3.01 seconds = 38.48 MB/sec
I'm using the Raspberry Pi Imager v1.7.2 to write the "USB Boot" utility to a spare microSD card. This changes the boot priority to prefer USB. https://www.tomshardware.com/how-to/boot-raspberry-pi-4-usb
Now I'm cloning the microSD that was booting this Pi onto the USB drive. I'm using balenaEtcher, which has a built-in clone workflow.
And, success!
/dev/sda2:
Timing buffered disk reads: 714 MB in 3.00 seconds = 237.88 MB/sec
@annika I'm glad to read that. I have a couple of Pi that I need to change from SD card boot to something with longer term stability. I was thinking of using a m.2 SSD in one of these cheap USB adapter cases.
That was painless, way simpler than I expected. It's possible the system already supported USB boot out of the box but I didn't think to check.