Linux

sgdisk --replicate=/dev/sda /dev/sdb
sgdisk --randomize-guids --move-second-header /dev/sd

mdadm --manage /dev/md1 --add /dev/sda2
mdadm --manage /dev/md2 --add /dev/sda3
mdadm --manage /dev/md3 --add /dev/sda4

Now I have a good mirror in place. Now the question is that when I try to boot the system using the New Hard disk /dev/sda from the BIOS, it comes to halt and nothing shows up except blinking cursor on blank screen and I have to reboot the system to select the /dev/sdb disk to boot from. This is happening for the normal reboot as well, in such a way that i have to select the disk manually everytime the system is rebooted. 

Can someone please guide how the other disk can be grub-recorgnized and how I can make a seamless reboot..

Below is the output from mdadmin --detail command


Code:
 mdadm --detail /dev/md{1..3}
/dev/md1:
        Version : 1.2
  Creation Time : Wed Jun  5 19:02:13 2013
     Raid Level : raid1
     Array Size : 19514240 (18.61 GiB 19.98 GB)
  Used Dev Size : 19514240 (18.61 GiB 19.98 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Sun Oct  6 01:00:02 2013
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           Name : busyboy:1  (local to host busyboy)
           UUID : 24d0bec2:c86a4b42:2551491c:ce21cac7
         Events : 50

    Number   Major   Minor   RaidDevice State
       0       8       18        0      active sync   /dev/sdb2
       2       8        2        1      active sync   /dev/sda2
/dev/md2:
        Version : 1.2
  Creation Time : Wed Jun  5 19:20:37 2013
     Raid Level : raid1
     Array Size : 488149824 (465.54 GiB 499.87 GB)
  Used Dev Size : 488149824 (465.54 GiB 499.87 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Thu Oct 10 13:47:44 2013
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           Name : busyboy:2  (local to host busyboy)
           UUID : ab235953:879428e8:d46af252:13ed66d3
         Events : 399197

    Number   Major   Minor   RaidDevice State
       0       8       19        0      active sync   /dev/sdb3
       2       8        3        1      active sync   /dev/sda3
/dev/md3:
        Version : 1.2
  Creation Time : Wed Jun  5 19:20:48 2013
     Raid Level : raid1
     Array Size : 2422320960 (2310.11 GiB 2480.46 GB)
  Used Dev Size : 2422320960 (2310.11 GiB 2480.46 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Thu Oct 10 13:47:46 2013
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           Name : busyboy:3  (local to host busyboy)
           UUID : 2a22160c:72b4f201:de0acb10:79566f08
         Events : 717493

    Number   Major   Minor   RaidDevice State
       0       8       20        0      active sync   /dev/sdb4
       2       8        4        1      active sync   /dev/sda4

# cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu 12.04.3 LTS"

# uname -a
Linux busyboy 3.5.0-23-generic #35~precise1-Ubuntu SMP Fri Jan 25 17:15:33 UTC 2013 i686 i686 i386 GNU/Linux

# dpkg -l |grep grub
ii  grub-common                      1.99-21ubuntu3.10                   GRand Unified Bootloader (common files)
ii  grub-gfxpayload-lists            0.6                                 GRUB gfxpayload blacklist
ii  grub-pc                          1.99-21ubuntu3.10                   GRand Unified Bootloader, version 2 (PC/BIOS version)
ii  grub-pc-bin                      1.99-21ubuntu3.10                   GRand Unified Bootloader, version 2 (PC/BIOS binaries)
ii  grub2-common                     1.99-21ubuntu3.10                   GRand Unified Bootloader (common files for version 2)