Re: [PATCH 01/19] btrfs: require at least 4 devices for RAID 6
flat view
From: David Sterba <hidden>
Date: 2026-05-12 11:42:42
Also in:
linux-arch, linux-arm-kernel, linux-btrfs, linux-crypto, linux-raid, linux-riscv, linux-s390, lkml, loongarch
On Tue, May 12, 2026 at 07:20:41AM +0200, Christoph Hellwig wrote:
While the RAID6 algorithm could in theory support 3 devices by just
copying the data disk to the two parity disks, this version is not only
useless because it is a suboptimal version of 3-way mirroring, but also
broken with various crashes and incorrect parity generation in various
architecture-optimized implementations. Disallow it similar to mdraid
which requires at least 4 devices for RAID 6.
Fixes: 53b381b3abeb ("Btrfs: RAID5 and RAID6")
Signed-off-by: Christoph Hellwig <hch@lst.de>This patch should have been sent separately as it has user visible impact and can potentially break some setups. The degenerate modes of raid0, 5, or 6 are explicit as a possible middle step when converting profiles. We can use a fallback implementation for this case if the accelerated implementations cannot do it.