Re: btrfs ontop of LVM ontop of MD RAID1 supported?

[Roman Mamedov <rm@romanrm.net>]

On Sat, 2 Mar 2024 15:01:43 +0000
Nigel Kukard <nkukard@LBSD.net> wrote:

> I'm wondering if btrfs ontop of LVM ontop of MD RAID1 is supported?  

Should be absolutely supported.

> I've managed to reproduce with 100% accuracy severe data corruption 
> using this configuration on 6.6.19.
> 
> 2 x 1.92T NVMe's in MD RAID1 configuration
> LVM volume created ontop of the MD RAID1
> btrfs filesystem on the LV
> 
> I then write about 100-200G of data. Create a snapshot. Read/write the 
> file and get these messages...

Has the MD RAID1 finished its initial sync after creation?

Have you tried waiting until it finishes and only then do thewrites to see if
the corruption is still observed (of course that's in no way a "workaround",
just to see what might cause the bug).

Do you know any kernel versions or series where this corruption did not happen?

I assume you're not saying it appeared in 6.6.19 compared to 6.6.18.

Can you try the 6.1 series? Or maybe also 6.8?

I made a Btrfs on top of LVM on top of RAID1 myself now, but on consumer SSDs.
Copying some files to it now, to check. Would be also helpful if you can find
a precise sequence of commands which can trigger the bug, less vague than
copy some files to it and see.

-- 
With respect,
Roman