[CentOS] RAID 1 not boot when disconnect a disk

[Aleksandar Milivojevic]

Quoting Roberto Pereyra <pereyra.roberto at gmail.com>:

> Hi
>
> I have a clean CentOS 4.4 disk and I have setup a RAID 1 with two  IDE disk.
>
> The system RAID 1  boot fine  but when I disconnect a disk (the first
> disk) the system not boot. The screen goes black and not boot anything
> (grub not boot).

Where is the Grub installed?  MBR or partition?

If you've setup RAID-1 during installation, Anaconda should have  
installed it in partition, which would mean that it got automatically  
mirrored to second drive.  If this is the case, most likely your BIOS  
is refusing to boot from second drive.  Also check that partition that  
holds /boot (usually first partition on the disk) is marked as  
bootable (use fdisk).

If you've installed on single drive, and setup RAID-1 after  
intallation manually chances are Grub is installed in MBR of first  
drive (Anaconda defaults to install Grub into MBR when installing on  
single drive).  If that is the case, than it won't be automagically  
mirrored to second drive.  You'll have to install it into second  
drive's MBR by hand, for example:

http://www.8-p.ca/archives/3-Grub-and-RAID-1.html