LVM RAID1 adding two more disks

Question

We have local server machine in our small company. Its running with Debian 8 on two 120GB SSDs merged in RAID1 with this tutorial. https://blogging.dragon.org.uk/installing-ubuntu-14-04-on-raid-1-and-lvm/

Now we want to add 2 more 1TB disks, merge them in RAID1 as another RAID volume and redirect GIT repos and some mysql backup dumps there.

Our setup looks like this

md2 : active (auto-read-only) raid1 sda3[0] sdb3[1]
2960384 blocks super 1.2 [2/2] [UU]

md1 : active raid1 sda2[0] sdb2[1]
113215488 blocks super 1.2 [2/2] [UU]
bitmap: 1/1 pages [4KB], 65536KB chunk

md0 : active raid1 sda1[0] sdb1[1]
975296 blocks super 1.2 [2/2] [UU]

unused devices: <none> 

Ive read some tutorial https://www.howtoforge.com/software-raid1-grub-boot-debian-etch

And now want to do this:

1. Create partitions on disks - sdc1 and sdd1
2. Set Linux raid autodetect type for them

3. Merge them in one volume

   mdadm --create --verbose /dev/md3 --level=mirror --raid-devices=2 /dev/sdc1 /dev/sdd1

4. Update mdadm.conf configuration

   cp /etc/mdadm/mdadm.conf /etc/mdadm/mdadm.conf_orig mdadm --examine --scan >> /etc/mdadm/mdadm.conf

5. Do the rest of work - set filesystem, add fstab line etc ...

Is this a good approach or is not as easy as im thinking? For example will there any troubles with GRUB?

Answer 1

That seems fine, a few comments...

--examine --scan is just a starting point, you should edit the mdadm.conf to make sure there are no duplicate entries, add a mail address, remove unnecessary stuff (array lines only need the device name and uuid, nothing else)

MAILADDR [email protected]
ARRAY /dev/md0 UUID=d8b8b4e5:e47b2e45:2093cd36:f654020d
ARRAY /dev/md1 UUID=845b2454:42a319ef:6ec5238a:358c365b
ARRAY /dev/md2 UUID=23cf90d2:c05d720e:e72e178d:414a8128

Linux raid autodetect is deprecated (no harm in using the partition type anyway, but it's not required), RAID is assembled by initramfs and you might have to update that whenever you change your mdadm.conf, fstab.