Re: What's the status of BTRFS RST instead of linux md raid5?

[Marc MERLIN <marc@merlins.org>]

On Mon, Apr 13, 2026 at 01:37:30PM +0200, Johannes Thumshirn wrote:
> 
> RST is still considered experimental and the development on the RAID5/6
> support is unfortunately delayed due to different more urgent fires that
> have to be extinguished.
> 
> Note while RST can handle non zoned devices, it's primary focus always was
> always to enable RAID on zoned block devices. Which it does for RAID0, RAID1
> and RAID10.
> 
> As for RAID5 I have a prototype doing writes and reads for the trivial cases
> (i.e. full stripe write/read).
> 
> 
> My apologies to everyone waiting for this. I haven't abandoned the project,
> I just need more time to get it done.
> 
> If you're looking for documentation please have a look here: https://github.com/kdave/btrfs-progs/blob/devel/Documentation/dev/design-raid-stripe-tree.txt

Thank you so much for the status update, *much* appreciated.
As for when, this is all unpaid work I assume, so it gets done when it
gets done, no worries.

For what it's worth, I've ben doing mdadm raid5 with btrfs since 2014,
and unfortuantely it's failed in too many ways, almost each time causing
a btrfs filesystem that was impossible to recover (usually ro mount was
ok, but impossible to get back in read/write state, which is very
inconvenient for a 20TB+ filesystem dueto how long it takes to restore
backups)

As luck would have it, this just happened to me again
https://yhbt.net/lore/linux-btrfs/advYoKqUCUmD4oO6@merlins.org/

I know I don't know the deep insides of the btrfs code, but it's
unfortunately failed enough times on top of mdadm raid5 that I can't
wait to switch to RST when it's ready.  It's been 12 years already, so I
can wait a bit longer still :)

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
 
Home page: http://marc.merlins.org/                       | PGP 7F55D5F27AAF9D08