DRBD kernel module mismatch in different distro's

[kees-closed]

Hi, I'm trying to understand something I've noticed in multiple distro's. That's that the kernel module is still version 8 and the userspace utilities are version 9. This software mismatch prevents me from using the connection mesh method, which is exclusively in DRBD 9.

I noticed this way back already, as described in here.

But this is still the case in Debian 11 as well:

drbdadm --version
DRBDADM_BUILDTAG=GIT-hash:\ baaca8a080dc54652f57da4bafb2dce51dfe9f68\ reproducible\ build\,\ 2020-09-29\ 09:05:36
DRBDADM_API_VERSION=1
DRBD_KERNEL_VERSION_CODE=0x08040b
DRBDADM_VERSION_CODE=0x090f00
DRBDADM_VERSION=9.15.0

And on Fedora 34:

drbdadm --version
DRBDADM_BUILDTAG=GIT-hash:\ a7820b3c14497a34f955ba5ce56cf1bc9d2d353e\ build\ by\ mockbuild@\,\ 2021-02-21\ 21:23:10
DRBDADM_API_VERSION=1
DRBD_KERNEL_VERSION_CODE=0x08040b
DRBDADM_VERSION_CODE=0x091000
DRBDADM_VERSION=9.16.0

What could be the reason for this? Is the kernel module not mature enough to be used? I suppose there is no way to use the connection mesh option when this old kernel module is used. The only alternatives would be to use the old stacking or build a module myself. Both not ideal.

[kees-closed]

I suppose it's because the DRBD9 kernel module isn't in the kernel mainline yet? I guess it will be "old school" stacking resources then :)

[rck]

A few things, maybe also for people finding this issue:

• it is fine to use drbd-utils 9.x with a kernel module 8.x. There is no "mismatch".
• kmod 9.x is mature enough, we recommend it for our customers, upstreaming is just a major effort. for sure that is the goal, but will not happen "tomorrow"
• building a module on your own is as complicated as calling make. One can even build a dkms package. But yes, it assumes a sufficiently compatible kernel (we build for around 100 kernels, the main LTS distributions/kernels should work). Still, it is additional work, depending if you distro provides a stable kABI or not, so you can become a customer and get access to LINBIT's software including prebuilt kernel modules.

[kees-closed]

• it is fine to use drbd-utils 9.x with a kernel module 8.x. There is no "mismatch".

I'll leave the following snippet here below for future generations to find, it might help them understand the severity of the error.

# /lib/drbd/drbdadm-84 --version
DRBD module version: 8.4.10
   userland version: 9.5.0
mixing different major numbers will not work!

Thanks for your reply by the way. I know that these solutions exist. I'll use the old stacking method in the meantime since I don't want to burden myself with maintaining and testing these kernel modules myself. Once it hits the mainline kernel I will switch. Thank you all for your hard work and dedication!

[rck]

there is no missmatch and there is no "severity on an error", you are just using it wrong. Why would you directly call the -84 version? The top level one handles that perfectly fine and calls the according tool depending on the kernel module loaded:

PATH=../v84:$PATH ./drbdadm --version  # using toplevel one, adding the -84 to the PATH in this case so it can be found and spawned
DRBDADM_BUILDTAG=GIT-hash:\ 35a7e9cbe29a14f3903d79c223997a948e77fd76\ build\ by\ roland@laubbaum\,\ 2021-04-30\ 14:15:18
DRBDADM_API_VERSION=1
DRBD_KERNEL_VERSION_CODE=0x08040b
DRBDADM_VERSION_CODE=0x091100
DRBDADM_VERSION=9.17.0
Ξ laubbaum drbd-utils/user/v9 master ✓ ../v84/drbdadm-84 --version # using it wrong for whatever reason
DRBD module version: 8.4.11
   userland version: 9.17.0
mixing different major numbers will not work!
DRBDADM_BUILDTAG=GIT-hash:\ 35a7e9cbe29a14f3903d79c223997a948e77fd76\ build\ by\ roland@laubbaum\,\ 2021-04-30\ 14:15:18
DRBDADM_API_VERSION=1
DRBD_KERNEL_VERSION_CODE=0x08040b
DRBDADM_VERSION_CODE=0x091100
DRBDADM_VERSION=9.17.0

[kees-closed]

The reason is just troubleshooting, since I get different versions of the userspace tools and kernel modules. Matching the userspace with the kernel module version (8.4) was just a way to test things and understand the tool. That error doesn't make it more clear. Please understand that this mixture of versions in a release is confusing for users as well. I hope the kernel module will be in sync soon then maybe with Debian 12 I can use the mesh functionality out of the box :)

[raltnoeder]

DRBD 8.x is limited to one replication link per resource. Multiple links require version 9.x, and that is also the reason why the connection-mesh section is only supported with a DRBD 9.x kernel module.