I installed CentOS 6.x 64 bit with the minimal ISO and used two disks in RAID 1 array.
Filesystem Size Used Avail Use% Mounted on
/dev/md2 97G 918M 91G 1% /
tmpfs 16G 0 16G 0% /dev/shm
/dev/md1 485M 54M 407M 12% /boot
/dev/md3 3.4T 198M 3.2T 1% /vz
Personalities : [raid1]
md1 : active raid1 sda1 sdb1
511936 blocks super 1.0 [2/2] [UU]
md3 : active raid1 sda4 sdb4
3672901440 blocks super 1.1 [2/2] [UU]
bitmap: 0/28 pages [0KB], 65536KB chunk md2 : active raid1 sdb3 sda3
102334336 blocks super 1.1 [2/2] [UU]
bitmap: 0/1 pages [0KB], 65536KB chunk md0 : active raid1 sdb2 sda2
131006336 blocks super 1.1 [2/2] [UU]
My question is if sda one fails will it still boot on sdb? Did the install process write the boot sector on both disks or just sda? How do I check and if its not on sdb how do I copy it there?