[Linux-cluster] Protocol compatibility of DLM/Corosync across versions

[Jan Friesse]

> Hi (again),
>
> Another question I have regarding DLM and Corosync (because Corosync is
> required to use DLM): should I expect compatibility across versions?

I will add just Corosync information.

Corosync with same major version is compatible (ie 2.3.0 works with 
2.4.0) but if major version differs it is incompatible (so no luck with 
1.4.2 vs 2.3.0). In 3.x we plan to (finally) to implement protocol 
(instead of sending 64-bit aligned C structures as it is now) so 
backwards/forwards compatibility should improve (but it also means that 
3.x is going to be incompatible with 2.x and 1.x).

For distribution versions. At least Fedora/RHEL has no extra patches for 
Corosync (eventho we may backport some fixes/features but never  breaks 
compatibility with upstream). I believe most of other distro works 
similar way. So as long as you keep Corosync versions close, Corosync works.


>
> I did a quick test between distributions running different kernels (CentOS
> 6, Centos7 and Ubuntu 14) but rather close versions of Corosync, and that
> test worked, but I am not sure if that was just luck. ;)
>
>
> Cheers,
> Jean-Marc
>