Previously I had a software raid set up using (mdadm) of drives sda and sdb. sdb failed and the only way to reboot the system was by unplugging the second hard drive.
Now I've added fresh sdb and sdc to my RAID setup. sda is the oldest (so most likely to fail) and it is the drive from which we boot (I think, how can I check?).
How can I ensure and test (through GRUB configuration, etc.) that if sda fails, I will still be able to boot my machine.
fdisk -l:
Disk /dev/sda: 250.0 GB, 250000000000 bytes 255 heads, 63 sectors/track, 30394 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: 0x00000080 Device Boot Start End Blocks Id System /dev/sda1 * 1 30064 241489048+ fd Linux raid autodetect /dev/sda2 30065 30394 2650725 5 Extended /dev/sda5 30065 30394 2650693+ fd Linux raid autodetect Disk /dev/sdb: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/sdb1 * 1 30064 241489048+ fd Linux raid autodetect Partition 1 does not start on physical sector boundary. /dev/sdb2 30065 30394 2650725 5 Extended /dev/sdb5 30065 30394 2650693+ fd Linux raid autodetect Partition 5 does not start on physical sector boundary. Disk /dev/sdc: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/sdc1 * 1 30064 241489048+ fd Linux raid autodetect Partition 1 does not start on physical sector boundary. /dev/sdc2 30065 30394 2650725 5 Extended /dev/sdc5 30065 30394 2650693+ fd Linux raid autodetect Partition 5 does not start on physical sector boundary. Disk /dev/md0: 247.3 GB, 247284695040 bytes 2 heads, 4 sectors/track, 60372240 cylinders Units = cylinders of 8 * 512 = 4096 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Alignment offset: 512 bytes Disk identifier: 0x00000000 Disk /dev/md0 doesn't contain a valid partition table Disk /dev/md1: 2714 MB, 2714238976 bytes 2 heads, 4 sectors/track, 662656 cylinders Units = cylinders of 8 * 512 = 4096 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Alignment offset: 512 bytes Disk identifier: 0x00000000 Disk /dev/md1 doesn't contain a valid partition table 
