[DRBD-user] .drbdctrl and resource roles

[Roland Kammerer]

On Thu, Nov 08, 2018 at 09:58:28PM +0200, Daniel Hertanu wrote:
> Hi,
> 
> Can someone help me understand the following situation? I have 3 nodes
> using DRBD9 with one node added without storage.
> 
> Now, on the two hosts with storage I have this:
> 
> [root at server2-drbd ~]# drbdadm status
> .drbdctrl role:Secondary
>   volume:0 disk:UpToDate
>   volume:1 disk:UpToDate
>   drbd-mon role:Secondary
>     volume:0 peer-disk:UpToDate
>     volume:1 peer-disk:UpToDate
>   server3-drbd role:Primary
>     volume:0 peer-disk:UpToDate
>     volume:1 peer-disk:UpToDate
> 
> res1 role:Primary
>   disk:UpToDate
>   server3-drbd role:Secondary
>     peer-disk:UpToDate
> 
> 
> 
> [root at server3-drbd ~]# drbdadm status
> .drbdctrl role:Primary
>   volume:0 disk:UpToDate
>   volume:1 disk:UpToDate
>   drbd-mon role:Secondary
>     volume:0 peer-disk:UpToDate
>     volume:1 peer-disk:UpToDate
>   server2-drbd role:Secondary
>     volume:0 peer-disk:UpToDate
>     volume:1 peer-disk:UpToDate
> 
> res1 role:Secondary
>   disk:UpToDate
>   server2-drbd.blinc.co role:Primary
>     peer-disk:UpToDate
> 
> 
> I would like to understand why, on server2, .drbdctrl role is secondary and
> res1 role is primary, while on server3 .drbdctrl role is primary and res1
> role is secondary.

Why not? A resource is Primary on that host that "uses" it. Auto-promote
with DRBD9 and an open(), or set to Primary.

> I can switch res1 primary role between server2 and server3 without problems
> but I can't do anything about .drbdctrl. Trying to change the role to
> secondary on server3 doesn't return any error but it's just not happening.

a) don't touch the control-volume. Drbdmanage, and only drbdmanage is
responsible to switch it Primary on a node. You do not do that manually,
DM selects one. You can stop all nodes, manually switch it to Primary on
your favorite host and then start all cluster nodes. Then you
"preselected" a leader node.

b) forget everything in a), remove drbdmanage, and install LINSTOR.

Regards, rck