When I reboot my server some of the disks become unavailable. This has happend since the beginning. the only way for me to get the disks back is to shutdown the server, wait a few seconds (or minutes in case of the diagnostics) and start the server by pushing the power button.

It is not a big inconvenience but slightly annoying and I fear that at one point it might cause some data loss, when fore example the array is able to start due to only one (ore two) missing drives.

the before reboot diagnostics are before the second reboot (shutdown, wait, power-up) and the after diagnostics after that.

Is there a way to slow down the reboot to keep this from happening, a BIOS setting or anything else I can do?

After Reboot.zip Before Reboot.zip

Disks are not being detected, curiously or not; they are the four WD 8TB drives. Other drives on the same controller show.

Try connecting those drives to the onboard SATA controller, swap with the ones currently there, then retest.