Re: [LSF/MM/BPF TOPIC] User space RAID5 with ublk and io_uring BPF

[Cong Wang <xiyou.wangcong@gmail.com>]

On Thu, Feb 19, 2026 at 01:38:46PM +0800, Xiao Ni wrote:
> Hi all
> 
> I'm doing some work on user-space RAID recently. I'd like to propose a
> topic for LSF/MM 2026 regarding the implementation of RAID5 in user
> space using ublk and io_uring bpf[1], particularly focusing on the
> challenges encountered and potential kernel improvements needed.
> 
> Ublk raid5 uses the ublk framework (tools/testing/selftests/ublk/),
> with the goal of leveraging io_uring's zero-copy capabilities and
> BPF[1] for performance optimization. The implementation includes:
> * RAID5 stripe handling with configurable chunk sizes
> * Multi-queue support via io_uring
> * Degraded mode for single disk failure tolerance
> * Integration with io_uring BPF struct_ops framework


This is very interesting.

Although technically different with RAID, how about user-space LVM?

I need it for the multikernel use case:
https://lpc.events/event/19/contributions/2074/attachments/1776/3957/Multikernel-LPC2025.pdf
(slide #19)

Relying on the in-kernel LVM is not ideal for provisioning since ublk is
already there.

Also, it does not need to be a complete replacement of existing LVM,
a simple ublk-defined storage isolation is sufficient.

Regards,
Cong Wang