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Upgrading a 2-node cluster to a 3-node cluster

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lverhoeven
Occasional Contributor

Upgrading a 2-node cluster to a 3-node cluster

Hello all,

I'm currently a the sistuation where I have three HP DL380's as a hypervisor. At the moment of the installation someone configured it in such a way that only one of these is used with local storage attached.

According to the design the machines should all share their storage using VSA so this is the situation I'd like to go to. To minimize downtime the idea is to configure VSA on the other two hypervisors and transfer the data to these machines. Once this is done the first machine can be added to the 2-node cluster we created. A fourth machine will be configured as the HP VSA FOM.

Could you please tell me if the above scenario is possible? Can we first create a 2-node cluster and than later add a 3rd node to it?

Best regards,

Luc

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oikjn
Honored Contributor
Solution

Re: Upgrading a 2-node cluster to a 3-node cluster

yes you can do exactly that.  Adding an additional node is something you can do on-line without production disruption, but it will initiate a LUN resync to redistribute the data across the three nodes evenly.

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pnorth
Occasional Contributor

Re: Upgrading a 2-node cluster to a 3-node cluster

Hello All
Sorry i'm so late to this thread, I just happen to stumble across this when searching how to add a 3rd node to a 2 node VSA cluster.

I would like to see if someone can explain the process of adding the 3rd node to the 2 node cluster.

Also, we use a FOM on a seperate server, my understanding is with a 3 node cluster you do not need a FOM on a seperate server.  What would be the process of moving the FOM into the 3 node cluster instead?  or is it recomended to keep the FOM seperate??

Thank you all for your help.

Paul.

 

Bart_Heungens
Honored Contributor

Re: Upgrading a 2-node cluster to a 3-node cluster

Hi,

The process is rather simple... Deploy a third VSA on a third server exactly the same as the 2 other VSA's, specifically the storage part. The third VSA needs to have at least the same capacity as the 2 others...

In the CMC console add the IP address of the third VSA first to the Management Group and afterwards at the cluster... At that moment all data will be restriped accross the 3 VSA's in the cluster. Therefore it is best to do this during low I/O moments like the weekend or overnight...

With 2 VSA's in a cluster you need indeed a FOM (tie breaker for quorum), with 3 VSA's a FOM is not supported so the FOM will need to be removed from the cluster before...

Bart

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Bianko
Occasional Advisor

Re: Upgrading a 2-node cluster to a 3-node cluster

For couriosity, does the RAID configuration (at VSA volume level) keeps the same? With two nodes you have a network RAID 10.. With 3 nodes cluster doesn't it need to be reconfigured as a RAID 5 or somewhat similar?

Bye,

Francesco

Bart_Heungens
Honored Contributor

Re: Upgrading a 2-node cluster to a 3-node cluster

Hi,

No it will stay Network RAID 10, being every block of data will be written on 2 nodes... For an example take a look at my article "Network RAID explained"

http://www.bitcon.be/a-closer-look-hp-storevirtual-networkraid-explained/

The picture shows an example with 4 nodes, but you can imagine the same for 3 nodes...

Kr,

Bart

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