Re: [Xen-devel] [BUG] Xen Remus, DRBD Protocol D and old Linux kernels

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

Just adding the Remus maintainers to the CC.

On Fri, 2016-01-15 at 15:26 -0300, Pato SÃinz wrote:
> Good evening, people.
> 
> More than a bug, it's an issue, a big one IMO.
> 
> Even though information on the Remus project and its implementation is kind of
> scarce on the internet and is usually outdated (the project could use some 
> love
> on that side of things, though it seems that on the coding side, it's
> still being
> properly maintained), there's a huge problem in the current implementation: 
> its
> storage depends on a custom patch developed for a very old version of DRBD.
> 
> Currently, the wiki points that in order to use Remus you must use it
> with a custom
> version of DRBD, forked from 8.3.11 (and there's also a patch for
> 8.3.9). Support
> for these versions have been dropped for almost 3 years, and they are only
> compatible with Linux kernels 3.0-3.4: most distros have already dropped these
> kernels and deleted them from their repositories: even kernel.org plans to 
> drop
> support for the 3.4 kernel in September this year. Building your own is an
> unnecessary hassle.
> 
> These problems make Remus practically unusable, despite being one of the
> coolest features Xen has in my honest opinion.
> 
> This issue has also been brought up at least once on the DRBD mailing list[1]
> and until there's more cooperation between the Xen project and LINBIT to
> develop a more robust Protocol D, they've refused to pull the patch into their
> tree to be maintained.
> 
> It's worth noting that the "official" patch (by rshiriam) is somewhat
> simple[2][3].
> 
> A solution to this for the short term would be to port the patch to the 
> current
> DRBD version (8.4.7-1) and in the long term, to collaborate with LINBIT so
> the Xen project doesn't have to maintain their own downstream changes, and
> we benefit from LINBIT's experience on realiable storage.
> 
> The short term solution seems like a very quick one, since the original patch
> is small-ish, and I've been trying to do it[4] but simply C isn't my strong 
> suit
> and I don't know much of DRBD's source, even after doing a cursory reading
> of it.
> 
> I know this is an open source project and thus most developers are
> volunteers, but
> this kind of issue really is a show-stopper that keeps me (and presumably many
> other people) from using the awesome feature that Remus is.
> 
> [1]: http://lists.linbit.com/pipermail/drbd-user/2013-October/020370.html
> [2]: 
> http://remusha.wdfiles.com/local--files/configuring-and-installing-remus/drbd-8.3.9-remus.patch
> [3]: 
> https://github.com/macrosheep/remus-drbd/commit/2685b294f5b416d827bdf446a69c88ab04df50dd
> [4]: https://github.com/superpatosainz/remus-drbd
> 

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