Citrix XenServer software raid 5 inactive after reboot - why?

Question

linux

For Citrix XenServer I set up software raid
mdadm --create --verbose /dev/md2 --level=5 --raid-devices=4 /dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3 then save mdadm
settings -
-examine --scan > /etc/mdadm.conf
And after
md2 reboot: inactive raid5 sda3[0] sdd3[3] sdc3[2] sdb3[1]
Only
mdadm --stop /dev/md2
mdadm --assemble helps - -run --force /dev/md2 /dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3
The raid is restored until the next reboot.