*Thanks for all, I did correctly grub-install /dev/sda and grub-install /dev/sdb , no error reported. Some friend said , there is a bug in grub2 of debian6 ?? may be, I checked grub from ubuntu, I got a problem too.
there is something strange; may be it helps, when I ran sfdisk -l, the second disk /dev/sdb had no identifier number (juste 0x00000) while /dev/sda had one. may be something bad was done by mdadm ? thanks a lot regards bela*
