I set up my raspberry to boot from external USB hard drive. It works, however when I turn on both raspberry and the disk at the same time, it fails. The disk needs more than 5 seconds to spin the discs probably. To fix that, I have to unplug raspberry from power socket and plug it again.Then it works.
I'd like to implement something what would do this for me automatically.
boot_delay doesn't help, because there is something needed to send a signal to the disk (eg. some read operation). When there is no read signal the disk goes to the idle mode and the discs stops spinning.
If there is no possibility to extend the boot_delay to more than 5 seconds, I'd like something to re-try booting on failure, eg. something what would restart the raspberry. Is it possible?