Frozen boot due to slow disk/controller

Im running ubuntu 20.04 on dell r740xd, One of the disk controller seem to present the disk(multipath disks used for openzfs pool) slow while the server is booting. If the server is boot from 'recovery mode'->'resume normal boot' the slow controller disk are detected and imported normally. until now i have tried to add rootdelay=300 option in grub cmdline options by editing file /etc/default/grub

GRUB_CMDLINE_LINUX_DEFAULT="rootdelay=300"
update-grub
update-initramfs -u

However i do not observe any delay and boot gets stuck

If the controller slot is disabled from the bios the server boots normally without using recovery mode(but its not an option).

PERC controllers should only boot after firmware initialization is completed, so I suggest you to double-check that no hardware issues are present. That said, you have at least two methods to delay boot:

• increase the time window where you can press CTRL+R to enter the controller's firmware (but latest gen PERC seems to have dropped this key combo)

• increase the Grub boot menu delay editing the option GRUB_TIMEOUT in /etc/default/grub and running update-grub (or equivalent command)