[DRBD-user] Why to specify node type?

[Robert Altnoeder]

On 5/11/19 8:45 PM, kvaps wrote:
> Hi, I still not get in why do we need to create special types of nodes
> in linstor, and do we need it?
>
> As can I see linstor supports next types of the nodes:
>
>  - Controller
>  - Auxiliary
>  - Combined
>  - Satellite

When LINSTOR was originally designed, it was considered an option that
multiple controllers would be running in an active-passive configuration
using their own cluster protocol, and if the active controller failed,
LINSTOR would execute a failover autonomously. For that reason, the
system had to know what the controller nodes are.

Satellites are nodes that the active controller needs to connect to.

Combined nodes are nodes that run a controller and a satellite process,
so a controller will still connect to those nodes' satellite software,
but it would also be aware of the available controller software on such
a node.

Auxiliary nodes are nodes that do not run any LINSTOR software, but may
run e.g. DRBD, so resources may be assigned to such nodes using LINSTOR,
and the controller would be able to generate e.g. DRBD configuration
files for the node, but the actual work on the node would have to be
done manually or by means of some other kind of software.

In the current implementation, the only nodes that the system really
needs to know about are the satellite nodes. The other node types can
still be used as a convenience option for administrators, so they can
look up which ones of their nodes have what kind of software installed.

br,
Robert