Centos 6 software raid-1 with EFI
Assuming that you are creating new OS setup. If you already have the centos installed on disk1 and want to add disk2 as software raid-1 refer to the official RHEL/centos documents you can find how to do it.
In centos 6 setup select to manually create volumes and create the identical by size partitions on both drives. The partition type should be "Software RAID" Leave the place (200-500 MB for the /boot/efi mount point on both disks , but select as mount point only for one) after that you be able to add raid devices [create the raid volumes] from the sda and sdb previously created partitions. So it should be something like this:
Device mountpoint type
--------------------------------------------
HardDrivers
/dev/sda
/dev/sda1 /boot/efi EFI Boot [vfat] #EFI mountpoint
/dev/sda2 {part0} Software RAID
/dev/sda3 Software RAID
/dev/sda4 {part1} Software RAID
/dev/sdb
/dev/sdb1 {same size as sda} EFI Boot #no mountpoint!
/dev/sdb2 {size -eq sda part0} Software RAID
/dev/sdb3 {size -eq sda swap} Software RAID
/dev/sdb4 {size -eq sda part1} Software RAID
Note that we have specified only 1 mountpoint for EFI boot.
While you creating each volume [raid device] you be able to select partiotions that will be mirrored , filesystem type and mountpoint After you add the Raid Devices and create raid partitions the next volumes should be added at the start of the list in centos 6 install GUI. So the "picture" will be like this :
Device mountpoint type
--------------------------------------------
RAID Devices
/dev/md0 / {part0} ext4
/dev/md1 swap
/dev/md2 /vz ext4
HardDrivers
/dev/sda
/dev/sda1 /boot/efi EFI Boot [vfat] #EFI mountpoint
/dev/sda2 {part0} Software RAID
/dev/sda3 Software RAID
/dev/sda4 {part1} Software RAID
/dev/sdb
/dev/sdb1 {same size as sda} EFI Boot #no mountpoint!
/dev/sdb2 {size -eq sda part0} Software RAID
/dev/sdb3 {size -eq sda swap} Software RAID
/dev/sdb4 {size -eq sda part1} Software RAID
As you can see currently EFI vfat partition not mirrored. But we have created the similar partition on sda1 and sdb1 . The mountpoint was configured only for sda1 (/boot/efi).
You can press "Next" and setup will continue. Once it will done login to your server .
Check mdstat:
cat /proc/mdstat
You should see the resync process. you can watch it live with watch command:
watch cat /proc/mdstat
Once resync will be done you can see the output like this:
cat /proc/mdstat Every 2.0s: cat /proc/mdstat Thu Mar 5
Personalities : [raid1]
md2 : active raid1 sda4[0]
1885593600 blocks super 1.1 [2/1] [U_]
bitmap: 6/15 pages [24KB], 65536KB chunk
md0 : active raid1 sda2[0]
51199872 blocks super 1.0 [2/1] [U_]
bitmap: 1/1 pages [4KB], 65536KB chunk
md1 : active raid1 sdb3[1] sda3[0]
16375808 blocks super 1.1 [2/2] [UU]
unused devices: <none>
Now you need to make manual mirror for /boot/efi. The next copmmands copy /boot/efi from sda to sdb:
dd if=/dev/sda1 of=/dev/sdb1 efibootmgr --create --disk /dev/sdb --label "CentOS Backup" --load "\\EFI\\redhat\\grub.efi"
Now you can disable sda in BIOS/EFI and check - system should load w/o any problems.
View status of SW RAID:
mdadm -D /dev/mdN
Also as I can understand in case of one HDD failure - after replacement you need to initiate manual resync from survived HDD to new like this {better refer original docs}: Force Manual Resync .stop array first:
mdadm --stop /dev/mdN
Perform resync:
mdadm --assemble --run --force --update=resync /dev/mdN /dev/sdX1 /dev/sdX1
ad/remove from md:
SDA1 hot remove
mdadm --manage /dev/mdN -r /dev/sda1 mdadm: hot removed /dev/sda1 from /dev/mdN
SDA add:
mdadm --manage /dev/mdN -a /dev/sda1 mdadm: added /dev/sda1
For more details about centos 6 software raid 1 install refer to the official guide : https://www.centos.org/docs/5/html/Deployment_Guide-en-US/s1-raid-config.html
