Re: Peanut gallery 2c

Kent Overstreet
2025-08-12T16:27:05Z

On Tue, Aug 12, 2025 at 11:24:18AM +0200, Johannes Thumshirn wrote:
> On Mon, Aug 11, 2025 at 12:08:12PM -0400, Kent Overstreet wrote:
> > I think bcachefs has been a bit of a kick in the pants for them, they've
> > taken some stuff directly from bcachefs - e.g. I believe they took the
> > basic design of raid5 v2, the stripes tree, directly from bcachefs. A
> > btrfs engineer asked me and I explained the design at a conference some
> > years back [...]
>
> Just one single mail and I will not reply to any follow ups on this. But I
> feel the need to clarify things as people have approached me. Yes Kent and I
> have talked about RAID. This has been at LSFMM 2024 in Salt Lake City.
>
> I can't remember if we talked about stripe trees, I only remember us talking
> about erasure coding, which Kent has done for bcachefs and I was planning to
> do for btrfs as well.
>
> But the 1st presentations I did on the idea of the stripe tree have been Lund
> Linux Conference and Plumbers in 2022 [1]. This is easy to look up. In the
> beginning the RAID stripe tree didn't have anything to do with RAID5 and the
> write hole at all (this is just a nice side effect) but with doing RAID on
> zoned block devices and ZONE APPEND writing.
>
> [1] https://lpc.events/event/16/contributions/1235/attachments/1111/2132/BTRFS%20RAID-DP.pdf

Thanks for the correction :)