External SSD Boot Speed
Although increasing the transfer speed from the SATA SSD at up to 400 MB/s to more than 1 GB/s halved the time taken to boot, there’s no consistent improvement beyond that. This suggests that time to boot an M1 Mac from an external SSD is around 5 seconds longer than from the internal SSD, and independent of SSD performance above 1.5 GB/s. This most probably reflects the lengthier process, in which early boot takes place from the internal SSD anyway, then transfers to the external SSD only after its LocalPolicy has been checked and applied.
Previously:
