I would like to have a Btrfs RAID1 setup using two different size drives without wasting any space.

Let sda be a 5TB drive and sdb a new 3TB drive.

Would it be possible to set this up as RAID1=[sda1=3TB partition]+[sdb=3TB drive], so that I can have [sda2=2TB partition]? Or does the whole (sda) drive have to be formatted as one Btrfs device (with no GUID partition table).

  • Yes, you can set up striping and mirroring using different size physical media, and leave the remainder on a larger drive for a non-raid partition. It does not matter how many drives, or what size drives you have. – ajeh Aug 2 '18 at 19:48
  • You can use sda or sda1 but see this answer of mine where I opt for the latter. – Kamil Maciorowski Aug 3 '18 at 6:17

BTRFS is just a filesystem. Just like any other filesystem, it doesn't care about the specifics of what device it's on, so, yes, you can do what you're asking about doing. Just don't try to run multiple partitions from the same physical device as part of the same BTRFS volume, performance will be horrible and you'll lose any data safety guarantees that whatever storage profile you are using would otherwise provide.

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