[DRBD-user] Down sync

[Robert Altnoeder]

On 7/23/20 4:06 PM, Roland Kammerer wrote:

> I don't know your write pattern, but this sounds like a bad idea.
> Multiple primaries are allowed during live migration where you can
> guarantee exactly one writer. Otherwise: don't do it.

I'll add some details:

Dual Primary is supported for two kinds of situations:

1. Temporary dual-primary for live-migration of VMs using a multi-node
replicated DRBD resource
2. Permanent dual-primary with specialized readers/writers (cluster file
systems, cluster-synchronized applications, etc.) on a two-node
replicated DRBD resource

You have a three-node replicated DRBD resource. Noone knows whether that
will replicate and resynchronize correctly even if it is connected.
In general, dual primary configurations are a lot less robust than
normal multi-resource active/active configurations and should be
avoided. In most cases, there are other configurations that do not
require dual primary mode for the same use-case, so in most cases, a
dual primary configuration is a misconfiguration in the first place.

Tell us more about what your actual use-case and applications are, and
we may be able to help you with the setup.

br,
Robert