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I have 2 hard drives with identical partitioning and RAID-1 between them. I want to break the mirror (OK with that), and then boot from the secondary side of the mirror without using Live-CD (that's important). Also, I do not have physical access to the server.

I tried to create new arrays with the secondary partitions (/dev/sdb*) and set grub and /etc/mdadm.conf but it doesn't work. I think I'm missing something.

Following is my partitioning (for sda, sdb is the same):
Disk /dev/sda: 64.4 GB, 64424509440 bytes
255 heads, 63 sectors/track, 7832 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00029482

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1         256     2048000   fd  Linux raid autodetect
Partition 1 does not end on cylinder boundary.
/dev/sda2   *         256         287      256000   fd  Linux raid autodetect
Partition 2 does not end on cylinder boundary.
/dev/sda3             287        3591    26534912   fd  Linux raid autodetect
/dev/sda4            3591        7833    34074624    5  Extended
/dev/sda5            3591        3846     2048000   fd  Linux raid autodetect
/dev/sda6            3846        4101     2048000   fd  Linux raid autodetect
/dev/sda7            4101        4356     2048000   fd  Linux raid autodetect
/dev/sda8            4356        4611     2048000   fd  Linux raid autodetect
/dev/sda9            4611        4866     2048000   fd  Linux raid autodetect
/dev/sda10           4866        5121     2048000   fd  Linux raid autodetect
/dev/sda11           5122        5377     2048000   fd  Linux raid autodetect
/dev/sda12           5377        5632     2048000   fd  Linux raid autodetect
/dev/sda13           5632        7283    13266944   fd  Linux raid autodetect
/dev/sda14           7284        7833     4413440   fd  Linux raid autodetect
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How was the RAID setup? Whole disks? (In which case it should 'just work' if you pull the first disk or use F12/boot select to boot from the second disk). Or with partitions in an array but not the whole disk. (Thus the boot information might be only on the first disk). (The way the post is written suggests the latter to me) –  Hennes Apr 22 '13 at 7:07
    
Thanks, Hennes. I updated my question in accordance to your comment. I do not have physical access to the server, and the whole disk is mirrored. –  Eran Ben-Natan Apr 22 '13 at 8:18
    
If I remember correctly, mdadm allows you to remove disks from a raid and mark them as "bad". –  Bobby Apr 22 '13 at 12:08
    
That's right, but how do I boot later from these "bad" disk/partitions? –  Eran Ben-Natan Apr 22 '13 at 12:50
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