Re: [SPDK] RAID1E POC Status

[David Butterfield <dab21774 at gmail.com>]

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On 9/22/19 9:42 AM, Luse, Paul E wrote:
> Still just a POC and a lot of work to do before we'd consider production worthy> if we decide to continue with it (I'll work on putting a list together over the next few weeks).

Are any of the Linux kernel RAID implementations considered good?

I have DRBD 9.0 running in usermode under SPDK as shown in this diagram:

    https://raw.githubusercontent.com/DavidButterfield/spdk/tcmu-runner/spdk_drbd.pdf

One possibility would be to port a kernel RAID module into the spot occupied by DRBD in the diagram.

The "port" of DRBD to run in usermode changes fewer than a dozen lines of code from the original source in the LINBIT repository.  Rather than changing the source code from the DRBD kernel module, its expected environment is simulated around it.  (This is intended to make it easier to update the usermode port to newer versions of the application as they appear.)

I did the same thing with SCST a couple of years ago.  I would expect the same to be possible for a kernel RAID module.  It won't just "drop in", because the set of emulated kernel functions has to be expanded to include whatever the RAID module uses that isn't already covered by the existing ports of SCST and DRBD.  I estimate it would take me one to two months of full-time work to get a kernel RAID module up and running well enough to be tested and used for experimentation.

Regards,
David Butterfield