[SOLVED] QDevice or two_node on 2-node cluster without HA

[stefanm]

Hi,

please forgive me if the following question was answered already and I just didn't get it when reading all the posts.

What I have is a small 2-node cluster without HA.
There are different suggestions to ensure that the remaining node keeps running in case that one node goes down.
Mainly:
Configure "two_node" and "wait_for_all" options for corosync or
Setting up a qdevice

I understand that qdevices are actually the preferred solution, but how is a qdevice better than the using the two corosync options if not aiming for a HA setup?

Thanks a lot for your help and sorry, if this is explained somewhere already!
Best

 

[t.lamprecht]

Hi,

I understand that qdevices are actually the preferred solution, but how is a qdevice better than the using the two corosync options if not aiming for a HA setup?

They are heuristics only, and allow only one node to fail, as some auto-tie breaker is required, which simply chooses the node with the lower ID (this is fixed info, so known for both even in split brain). So if the second node goes done your lucky, else not so.
QDevice handles both.

If you mean your setup serious I would heavily recommend an external QDevice or a third node over those options.

 

[stefanm]

Hi Thomas,
thanks a lot for your quick reply. This was exactly the information that I was missing.
Best regards!

 

[uldise]

Hi @t.lamprecht , i have a side question about qdevice - i have two small 2-device clusters in one LAN - production and test. can i use one qdevice running on external hardware for both clusters?
Thanks!

 

[narrateourale]

Hi @t.lamprecht , i have a side question about qdevice - i have two small 2-device clusters in one LAN - production and test. can i use one qdevice running on external hardware for both clusters?
Thanks!

AFAIK this should be possible

 

[uldise]

i'm asking cos when i tried to add second qdevice, process ends with errors.