[HECnet] OpenVMS 6.1 Cluster - Alpha not booting to form cluster

[Hans Vlems]

Van: Mark Wickens
Verzonden: dinsdag 8 oktober 2013 14:37
Aan: hecnet at Update.UU.SE
Beantwoorden: hecnet at Update.UU.SE
Onderwerp: Re: [HECnet] OpenVMS 6.1 Cluster - Alpha not booting to form cluster


On 08/10/2013 12:15, Brian Schenkenberger, VAXman- wrote:
> Mark Wickens <mark at wickensonline.co.uk> writes:
>
>> On 08/10/2013 11:33, Brian Schenkenberger, VAXman- wrote:
>>> Mark Wickens <mark at wickensonline.co.uk> writes:
>>>
>>>> Just wondered if anyone would know why my Alpha when booting hangs at
>>>> the point where it attempting to determine whether to join or form a VMS
>>>> cluster? It is clustered with a VAX - if I boot the VAX first the VAX
>>>> creates a cluster which the Alpha will then happily join when turned on,
>>>> but if I power the Alpha without the VAX it just hangs.
>>>>
>>>> Both are running an install straight from an original VMS 6.1
>>>> installation disk.
>>> Just 2 nodes?
>>>
>>> What's your quorum configuration?
>>>
>>> Post:
>>>
>>> $ MCR SYSGEN SHOW VOTES
>>> $ MCR SYSGEN SHOW EXPECTED_VOTES
>>>
>>> ..from each node.
>> I think you, sir, may have found the issue:
>>
>> On RIPLEY (the Alpha):
>>
>> $ mcr sysgen show votes
>> Parameter Name Current Default Min. Max. Unit Dynamic
>> -------------- ------- ------- ------- ------- ----
>> -------
>> VOTES 1 1 0 127 Votes
>> $ mcr sysgen show expected votes
>> Parameter Name Current Default Min. Max. Unit Dynamic
>> -------------- ------- ------- ------- ------- ----
>> -------
>> EXPECTED_VOTES 2 1 1 127 Votes
>>
>>
>> On DALLAS (the VAX):
>>
>> $ mcr sysgen show votes
>> Parameter Name Current Default Min. Max. Unit Dynamic
>> -------------- ------- ------- ------- ------- ----
>> -------
>> VOTES 1 1 0 127 Votes
>> $ mcr sysgen show expected votes
>> Parameter Name Current Default Min. Max. Unit Dynamic
>> -------------- ------- ------- ------- ------- ----
>> -------
>> EXPECTED_VOTES 1 1 1 127 Votes
>
> OK. First, 2 node clusters can be problematic due to not realy having the
> necessary number of node to properly form a cluster. The minimum is three
> nodes to form a cluster.
>
> However, let's look at what you said.
>
> You said that the VAX boots and forms a cluster. It has one vote and the
> expected votes is one. Therefore, when you boot it, it sees the necessary
> number of votes to continue booting and form a cluster.
>
> You also said that Alpha boots and hangs trying to form a cluster. It too
> has one vote but its expected votes is two. Therefore, until the VAX has
> booted, the number of votes is not present and the Alpha will hang.
>
> If you lower expected votes, the Alpha wil boot just like the VAX does. I
> would caution you read the VMS documentation regarding clusters and how to
> determine quorum. You risk, in the configuration of two nodes where each
> has one vote and expected votes of one, partitioning the cluster resulting
> in data corruption.
>
Thanks for the reminder of these issues. To be honest my experience with 
clustering is limited and generally specific to satellite based 
configurations. In this case I may make the VAX a satellite of the Alpha 
with the local disk acting as page/swap.

Am I right in thinking then that the relationship changes somewhat in 
that the Alpha will always need to be up but the VAX can come and go as 
it pleases (with the correct shutdown sequence)?

Regards, Mark.

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