RHEL 6 /boot redundancy

Latest response

Hi All,

I have a RHEL 6 system which utilises a software mirror for the logical volumes to provide a level of redundancy. Due to the limitations of not being able to software RAID /boot, it is on its own file system on another disk.

As luck would have it the disk with /boot on it was the one that has just decided to die so I am going to have to recreate it on another disk. It's got me wondering if there is a way of providing a level of redundancy for /boot on systems that don't have any other redundancy for that file system (e.g. hardware RAID)?

Thanks

Aidan

Responses

Hi Aidan,

LVM mirror is not possible for /boot, but mdadm software raid is available.

Kind regards,

Jan Gerrit Kootstra

Yep..what Jan said ;-)

Here is a kickstart example I found fairly quickly:

part raid.01 --size=128  --ondisk=sda
part raid.02 --size=8192 --ondisk=sda
part raid.03 --size=3072 --ondisk=sda
part raid.04 --size=512  --ondisk=sda

part raid.05 --size=128  --ondisk=sdb
part raid.06 --size=8192 --ondisk=sdb
part raid.07 --size=3072 --ondisk=sdb
part raid.08 --size=512  --ondisk=sdb

raid /boot --level=RAID1 --device=md0 --fstype=ext2 raid.01 raid.05
raid /     --level=RAID1 --device=md1 --fstype=ext3 raid.02 raid.06
raid swap  --level=RAID1 --device=md2 --fstype=swap raid.03 raid.07
raid /tmp  --level=RAID1 --device=md3 --fstype=ext3 raid.04 raid.08

Personally - I would still use LVM .. but you get the idea.

EDIT: credit due to
https://wiki.nikhef.nl/grid/RAID-1_configuration_and_management

In our operation, our root drives are RAID-protected (most of our Linux systems are VMs, but our physical instances are all on servers with hardware RAID controllers and disks). We primarily use LVM on the root volumes to improve partioning-flexibility.

That said, there's at least a couple ways to attack the problem (if your system can't do it in hardware or you don't want to do it in hardware):
* use mdadm to create a software RAID that GRUB can work with
* Set up two grub-entries per hosted OS - one pointing to hd0 and one pointing to hd1 - and then using an automated job to keep your main "/boot" synced to your standby "/boot"

Thanks for the suggestions. I'm not quite sure how I got the wrong end of the stick regarding /boot and software raid! I've set up a new RAID 1 for boot and it's working fine.

Aidan