[CentOS] Booting Software RAID

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[0] sdb1[1]
      511936 blocks super 1.0 [2/2] [UU]
md3 : active raid1 sda4[0] sdb4[1]
      3672901440 blocks super 1.1 [2/2] [UU]
      bitmap: 0/28 pages [0KB], 65536KB chunk
md2 : active raid1 sdb3[1] sda3[0]
      102334336 blocks super 1.1 [2/2] [UU]
      bitmap: 0/1 pages [0KB], 65536KB chunk
md0 : active raid1 sdb2[1] sda2[0]
      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?