On Wed, Jun 20, 2012 at 2:18 AM, <m.roth at 5-cent.us> wrote: > Rob Kampen wrote: >> On 06/20/2012 07:23 AM, Arun Khan wrote: >>> On Wed, Jun 20, 2012 at 12:11 AM,<m.roth at 5-cent.us> wrote: >>>> Arun Khan wrote: >>>>> Device Boot Start End Blocks Id System >>>>> /dev/sda1 * 1 523 4194304 83 Linux >>>>> Partition 1 does not end on cylinder boundary. >>>>> /dev/sda2 523 1045 4194304 83 Linux >>>>> /dev/sda3 1045 1176 1048576 82 Linux swap / >>>>> Solaris >> raid needs Id of fd rather than 83 to auto detect?? > > Good catch. A quick google got me a page on filesystem types, which had > this line: > fd Linux raid partition with autodetect using persistent superblock > But this is supposed to be RAID1 on the *entire* disks and not on the individual partitions. The instruction on the wiki clearly states do a "regular" install on the first disk (I did leave a few blocks at the end of the first disk as per the instructions) and then create a "partitionable" RAID1 md_d0. <http://wiki.centos.org/HowTos/Install_On_Partitionable_RAID1> <wiki quote> .............. Why would you want to have a system installed on a partitionable software RAID1? If you are installing a system on a partitionable RAID you can use the whole hard drive as a RAID component device, and since RAID1 is a mirror, you will be able to boot your system from any of the drives in case of failure without any additional tricks required to preserve bootloader configuration, etc. And when you need to repair a failed RAID volume with the whole hard drive as a RAID component, all you have to do is to insert a new hard drive and run mdadm --add; no partitioning or anything else required. ........... Steps for both CentOS 5 & 6 1. Install CentOS using standard installer on the first hard disk, /dev/sda. Select manual partitioning during the installation, and leave at least 1 unit at the very end of the disk unpartitioned. You will be able to redeem most of this space back later. You need to reserve this space for mdadm which stores it's metadata at the last chunk of a raid volume. 2. Boot from the CentOS installation disk in the Rescue mode. The installer will ask you if you wish to mount an existing CentOS installation, you must refuse. 3. Build the software RAID1 using mdadm in degraded mode, with /dev/sda as the only drive: mdadm --create --metadata=0.90 --level=1 --raid-devices=2 /dev/md_d0 /dev/sda missing 4. Add the mirror drive /dev/sdb into the raid and check /proc/mdstat to see that the raid started building: mdadm --add /dev/md_d0 /dev/sdb cat /proc/mdstat ........... </wiki quote> -- Arun Khan