>> 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? > no, you need to run grub-install /dev/sdb manually > keep in mind you need to do the same after replace a disk > the first part of grub is outside the RAID itself in the MBR # file -s /dev/sda /dev/sda: x86 boot sector; GRand Unified Bootloader, stage1 version 0x3, boot drive 0x80, 1st sector stage2 0x849fc, GRUB version 0.94; partition 1: ID=0xee, starthead 0, startsector 1, 4294967295 sectors, extended partition table (last)\011, code offset 0x48 # file -s /dev/sdb /dev/sdb: x86 boot sector; GRand Unified Bootloader, stage1 version 0x3, boot drive 0x80, 1st sector stage2 0x849fc, GRUB version 0.94; partition 1: ID=0xee, starthead 0, startsector 1, 4294967295 sectors, extended partition table (last)\011, code offset 0x48 I am guessing this is saying its present on both? I did nothing to copy it there so it must have done it during the centos 6.x install process.