Question

10

How to install using btrfs in RAID10 mode?

rated 0 times [ 10] [ 0] / answers: 1 / hits: 9604 / 1 Year ago, wed, march 29, 2023, 10:23:41

As a test I want to install Ubuntu 11.10 onto a btrfs file system in raid10 mode.
However, I have no clue on how I should go about that.
I have tried the installer, and then creating the fs in the terminal. However, that didn't work out.
When I went back to the graphical interface I couldn't install. Because it didn't have any mount points.
So, how should I do this?

After using the alternate installer and dropping to a shell I did the following:
mkfs.btrfs -m raid10 -d raid10 /dev/sda /dev/sdb /dev/sdc /dev/sdd
then you also need to run:
btrfs dev scan

Then when choosing the partition to install to, select one of the above and mount that to /. Leave all partitions untouched.

This installs the system, however, installing the bootloader fails...

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answered 1 Year ago dersol · Accepted Answer

OK, part of my problem was that I wanted to install Ubuntu Server.
I have finally succeeded. To install Ubuntu Server on btrfs RAID10, use the following steps:

Run the livecd of Ubuntu Desktop

Use gparted to create btrfs partitions on all the disks you want to use in the btrfs RAID10 setup, be sure to leave 1 MB at the beginning of the disks for GRUB. (I leave 1 MB on all the disks, so that I could always move grub to another disk, when I replace a disk with a new/larger one.

Save the new partition table

shutdown

launch the Ubuntu server installer

at the partitioning step, break out of the installer and go to the terminal

in the terminal type the following command to create a btrfs RAID10 for data and metadata (Note use the partitions, not the disks!):
```
mkfs.btrfs -m raid10 -d raid10 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1
```

IMPORTANT: execute the following command: btrfs dev scan

go back to the partition part of the installer

select any one disk and choose to use that as btrfs and mountpoint root

proceed installer as normal

So this works fine, however, I later found out that this does not do what I had expected.
I have 16-G, 500G and 2x 750G hard disks.

I expected to be able to use 910G. However, raid is a bit different in btrfs I got 320G. What I wanted to use is raid1, because this will create 2 copies of each data block, even if you add 4 disks (unlike the normal raid1). So now, using raid1 in btrfs I do get the 910G.