I'm very new in the Linux world and I find it very appealing so I decided to buy a rackable server to use it to learn more (it's a very old Dell R710 which i found very cheap but I find it perfect for what my needs rather than going to a junkyard).
Before actually starting to use it, I'm doing a RAID 1 test on virtualbox. My plan is to have two SSDs in the server setup as RAID 1 that will have Ubuntu installed on them.
I found various guides on how to setup a raid 1 on two drives that are also os/boot drives but i didn't have much luck in finding what to do in case one of them fails, respectively how to rebuild a failed RAID 1 drive that's also an os/boot drive.
In virtualbox, i added two 10GB drives and in Ubuntu server installed, i selected:
- Custom storage layout
- Drive 1 > Use as boot device
- Drive 1 free space > add GPT partition > format [leave unformatted] & mount [/]
- Drive 2 > Add as another boot device
- Drive 2 free space > add GPT partition > format [leave unformatred] & mount [/]
- Create software raid > RAID level 1 / added both partitions
After installation, i can see this:
root@vm:~# cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb2[0] sda2[1]
10473472 blocks super 1.2 [2/2] [UU]
unused devices: <none>
root@vm:~# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
loop0 7:0 0 111.9M 1 loop /snap/lxd/24322
loop1 7:1 0 63.3M 1 loop /snap/core20/1822
loop2 7:2 0 49.8M 1 loop /snap/snapd/18357
sda 8:0 0 10G 0 disk
├─sda1 8:1 0 1M 0 part
└─sda2 8:2 0 10G 0 part
└─md0 9:0 0 10G 0 raid1 /
sdb 8:16 0 10G 0 disk
├─sdb1 8:17 0 1M 0 part
└─sdb2 8:18 0 10G 0 part
└─md0 9:0 0 10G 0 raid1 /
sr0 11:0 1 1024M 0 rom
Now i shut down the vm, removed a disk vdi and created a new one, again of 10 GB. This will simulate the failure of one of the SDDs and replacing it with a new, empty one.
After booting again, i got this:
root@vm:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sda2[1]
10473472 blocks super 1.2 [2/1] [_U]
unused devices: <none>
So what i did next is:
root@vm:~# sfdisk -d /dev/sda | sfdisk /dev/sdb
/dev/sdb1: Created a new partition 1 of type 'BIOS boot' and of size 1 MiB.
/dev/sdb2: Created a new partition 2 of type 'Linux filesystem' and of size 10 GiB.
root@vm:~# fdisk -l
Disk /dev/sda: 10 GiB, 10737418240 bytes, 20971520 sectors
Disk model: VBOX HARDDISK
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 087509D7-06F6-4346-BA97-7A0E0D303D9D
Device Start End Sectors Size Type
/dev/sda1 2048 4095 2048 1M BIOS boot
/dev/sda2 4096 20969471 20965376 10G Linux filesystem
Disk /dev/sdb: 10 GiB, 10737418240 bytes, 20971520 sectors
Disk model: VBOX HARDDISK
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 087509D7-06F6-4346-BA97-7A0E0D303D9D
Device Start End Sectors Size Type
/dev/sdb1 2048 4095 2048 1M BIOS boot
/dev/sdb2 4096 20969471 20965376 10G Linux filesystem
So they appear to be identical now so next, i did:
root@vm:~# mdadm --manage /dev/md0 --add /dev/sdb2
root@vm:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb2[2] sda2[1]
10473472 blocks super 1.2 [2/1] [_U]
[================>....] recovery = 81.2% (8508864/10473472) finish=0.1min speed=202005K/sec
unused devices: <none>
Now, lsblk looks exactly like it did when i started.
Next, I tried rebooting and going in virtualbox boot menu (F12). Here, choosing disk 1, boots just fine but choosing disk 2 complains about not having a boot loader. So i booted from disk 1 and did:
root@vm:~# sudo grub-install /dev/sdb
root@vm:~# sudo update-grub /dev/sdb
And now it seems to be booting off either drive. I also created a file before replacing the drive and this file now shows up regardless of which drive i boot from.
So it kinda works, but is this the correct way to do it?
Am i missing something that could go wrong once i setup the actual SSDs in the server?
Thank you very much and sorry for the long post but maybe someone else will find it helpful.
