[Linux-cluster] A few GFS newbie questions: journals, etc

[Patrick Caulfield]

Nate Carlson wrote:
> On Wed, 29 Jun 2005, Patrick Caulfield wrote:
> 
>> Can you be more explicit please ? When another node comes online it
>> should set the expected_votes to be 50 regardless of any manual
>> intervention. Is that not what is happening ?
> 
> 
> Here's relevant snippets from my cluster.conf:
> 
> <cman expected_votes="10">
> </cman>
> 
> <clusternode name="xen1.msp.technicality.org" votes="50">
> </clusternode>
> 
> <clusternode name="xen2.msp.technicality.org" votes="50">
> </clusternode>
> 
> <clusternode name="xen-vm-1.msp.technicality.org" votes="1">
> </clusternode>
> 
> I can bring xen1 or xen2 online without any other nodes online, and get
> quorum. Once both nodes are online, though, cman_tool status says:
> 
> Nodes: 2
> Expected_votes: 10
> Total_votes: 100
> Quorum: 51
> 
> ..so the quorum value is being raised to 51, which is half+1 of
> Total_votes, not the Expected_votes (which would be what I'd expect, but
> again, I'm a newbie.)

That is right. What you have here is cman correcting an incorrect configuration.
You've told it to expect only 10 votes but provided it with 101 votes. It knows
when you're lying to it ;-)

> What I'd really like is a way to lock the quorum
> number down to 10 (at all times), so if any physical node is surviving
> the cluster will be up. Is there any simple way to do that?

What you actually have here is a special case of a two-node cluster, because
there are only two "real" nodes involved. Unfortunately the cman "two_node" mode
is no use here because it enforces the 2-node restriction which would prevent
you bringing any VMs online once the two real machines were up.

One little-known feature is that you can set votes to zero (only in CCS, not
from the cman_tool command-line) which may go a little way to helping out. it
would, at least, work for 3 or more Xen host nodes if all the VMs had zero votes.

Perhaps we should change "2-node" mode to allow >2 nodes provided the extra
nodes all had zero votes ?

-- 

patrick