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?