[DRBD-user] Do You Always Have to Upgrade/Rebuild DRBD Whenever You Upgrade the Kernel?

[Eric Robinson]

> -----Original Message-----
> From: drbd-user-bounces at lists.linbit.com <drbd-user-
> bounces at lists.linbit.com> On Behalf Of Roland Kammerer
> Sent: Monday, April 25, 2022 1:40 AM
> To: drbd-user at lists.linbit.com
> Cc: Roland Kammerer <roland.kammerer at linbit.com>
> Subject: Re: [DRBD-user] Do You Always Have to Upgrade/Rebuild DRBD
> Whenever You Upgrade the Kernel?
>
> On Fri, Apr 22, 2022 at 09:05:46PM +0000, Eric Robinson wrote:
> > Thanks for the feedback, Roland. I am actually a paying Linbit
> > customer, but I am unaware of the process to follow when upgrading the
> > OS. For example, I'm currently running Rocky Linux 8.5 (kernel
> > 4.18.0-348.2.1.el8_5.x86_64) and drbd 9.19.1-1.el8.
>
> The name of the meta package (i.e., "drbd") is IMO pretty unfortunate, that
> version refers to DRBD utils. It does not matter, can not remember when we
> did a breaking change in utils. What matters is kmod-drbd. But you most
> likely know that.
>

Indeed. We've been using DRBD since 2006. We're not experts, but we've picked up a few of the basics. 😊


> > There is a kernel
> > upgrade to 4.18.0-348.20.1.el8_5 available in the Rocky repo. If I
> > install that, does it break drbd?
>
> In 99.9% it does not break the binary module. That would only be the case if
> the vendor broke the kAbi. We usually have 1 binary module per RHEL dot
> release. So as long as you don't jump from like RHEL 8.4 to 8.5 or something
> then the same module should be fine. Also, you might enable a "dot
> repository" (one that has .../rhel8.5/... in the URL, not the global
> ".../rhel8/..." one that contains all the kernel modules for all RHEL (8.0, 8.1,
> 8.2,...) if you are a customer. If you enabled the "dot repo" you should be
> fine taking the latest kernel + the latest kmod-drbd. If, and that is very
> unlikely, there are more than 1 kmod-drbd in a dot repo, use the one closest
> to your kernel version, usually the later one. Again, that usually is not the
> case, only if the kAbi was broken.
>
> Finding the best matching kernel module to a given kernel for all DRBD
> modules that exist is a problem we had to solve ourselves, we even have a
> public web service one can use like this:
> $ cat /etc/os-release | curl -T - -X POST drbd.io:3030/api/v1/best/$(uname -r)
> -s
>
> At the time of writing it answered with:
> kmod-drbd-9.1.7_4.18.0_348-1.x86_64.rpm
>
> If you are into RHEL versioning, you see that this is the first kernel-devel
> package in that kernel series. So, for 4.18 there has not been any breakage.
> Which again is the usual case, the people at Redhat know what they are
> doing. Most of the time :).
>
> Code for that web service and the underlying python library can be found
> here:
> https://github.com/LINBIT/bestdrbdmodule
> https://github.com/LINBIT/python-lbdist
>
> Regards, rck

This is all excellent information, thanks much.

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