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I taught I have to install the grub on the raid array, thus the grub will put a copy of itself on the first partition on both hard drives, used for the raid1, right?
Wrong AFAIK. You can do that IF you have a boot loader on the MBR pointing to grub. BIOS does not read software raid and knows nothing about software raid. Software raid does not come into play until the kernel via initrd is loaded. Install to the MBR of the first HD of the array, then use grub to install into the MBR of the other members. If I am wrong, then it is news to me, but hey, I will learn new things! See my old "howto" on Linux, grub and raid at damtek.com for the exact commands. It is not pretty, but it will work.
HTH -- Damon L. Chesser damon@damtek.com http://www.linkedin.com/in/dchesser