BTRFS RAID1, totally useless?

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HellrazorX

Member
Oct 14, 2021
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Hello everyone,
To get this thing out of the way first. I know BTRFS is presented as an experimental feature and RAID5 or + is strongly discouraged.

However, BTRFS is one of the available options when installing. I though it would be safe to use RAID1

I tested with two virtualize instances of PVE and got different results, there's one thing for sure:
A vanilla proxmox install on BTRFS raid 1 cannot boot if disk 2 is disconnected...

Does anybody can share their experience when running Raid1 btrfs as Root disk for PVE?
 
HellrazorX said:
A vanilla proxmox install on BTRFS raid 1 cannot boot if disk 2 is disconnected...
Click to expand...
As I understood from another thread, this is "normal BTRFS behavior" and you need to set some BTRFS kernel parameter have it work in a degraded state.
From the Arch Wiki:
You will get the same error if you try to mount a raid array without one of the devices. In that case, you must add the degraded mount option to /etc/fstab. If your root resides on the array, you must also add rootflags=degraded to your kernel parameters.
Click to expand...
 
leesteken said:
As I understood from another thread, this is "normal BTRFS behavior" and you need to set some BTRFS kernel parameter have it work in a degraded state.
From the Arch Wiki:
Click to expand...
Sure. I did this.
This is why I'm asking users to share their experience.
I'm talking about going to the full process of changing a disk etc.
I simply feel like nobody is using it.

After all the time I spent, trying to do so, I ended up with inconsistent/unreliable results.
1. Build raid
2. Change grub, fstab
3. Remove disk fall to rescue mode
I tried DD some stuff out, rebuild btrfs, rebuild grub etc etc repeat
Sometimes I ended up with broken fs (proxmox boots but crashes)

Documentation lacks from everywhere also.
I really wanted to use btrfs, but if I can't find a concise recipe to change a simple disk.
Even if there is, having to change grub cfg and stuff scares me, will have to check back every upgrades...

I'm already switching back to zfs.
 
I run BTRFS RAID-1 on boot drives on 12-year old servers for RAM reasons.

Only run it on equipment you can recover from or don't care about.
 
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