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Re: btrfs: mixing raid0 and raid1 - How?

On 04/16/2016 12:00 AM, Matthias Bodenbinder wrote:
I have 3 hard drive with 750 GB, 500 GB and 250 GB. I want to use btrfs as filesystem. This will be my first test installation of btrfs.

My target is to get redundancy as well as a 750 GB data capacity. So I was thinking to create a raid0 with the 500 and 250 GB drive. This would result in a raid0 with 750 GB capacity. I want to add this raid0 as a mirror in a raid1 with the other 750 GB drive.

But how do I do that?

250 GB HDD + 500 GB HDD can yield:
- 250 GB RAID0,
- 250 GB RAID1, or
- 750 GB JBOD.

To get 750 GB RAID0 or 750 GB RAID1, you need two 750 GB devices.

As other posters have mentioned, btrfs is fairly new on Linux and Debian. I run Oldstable (Wheezy), and btrfs seems to mostly work as a file system (OOTB, btrfs root works, but GRUB can't read btrfs /boot). You may have to run a newer Debian and/or a newer kernel to get a btrfs with volume management and/or better Debian integration.

LVM has been stable on Debian for many years. I used it in the past to create a 250 GB HDD + 250 GB HDD + 300 GB HDD => 800 GB JBOD, so LVM can certainly create a 250 GB HDD + 500 GB HDD => 750 GB JBOD. I assume LVM can also create a 750 GB HDD + 750 GB JBOD => 750 GB RAID1. The challenge would be setting everything up so that the 750 GB RAID1 comes up automagically at boot and tears down cleanly at shutdown.

mdadm is another stable technology that could work in your case.


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