Hi all,
i'm writing this post simply to help those guys who are having problem starting raid because i have spent a day of my life understanding why the hell my raid doesn't work after system rebooting.


*******************WARNING*************
following this procedure can delete all your data




THE PROBLEM IS:
you are creating a raid (for example raid1).
after modified RAIDTAB you launch mkraid command and
then verify the file /proc/mdstat.
All is ok but the next time you boot.....INVALID ARGUMENT!!! and if you look in the log file messages you see BAD SUPERBLOCK MAGIC.

Is some posts i have seen that some guys have solved the problem by starting raid using raidstart --all because they have discovered that the problem was that linux didn't start automatically raid.

But this is not the case. I receive this error even with raidstart --all, and, however, this error occurs with every disk I use to create a raid, scsi, ide, etc....


SOLUTION:
I have seen that you can work around this problem by setting to 1 the option in RAIDTAB called
"persistent superblock"

Doing this the error doesn't appear anymore.


TEST:
For 2 or 3 times i have tried to reset the option again to 0 and to remake the raid. I have always received the same error after linux reboot. Resetting again the option to 1 and remaking the raid,cause it corretly works even after reboot (REMEMBER however to launch the command "raidstart --all" because it is not sure that linux will do it for you).


NOTE: if i have correctly understood, this option "persistent superblock" makes raid disks visible to the kernel even if you change their SCSI position. I know that this is strange and that can be not directly related to the problem, but it works very well, so, let's do it!!


I hope this will be useful for you

Bye bye!!