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Multi nodes cluster

 
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Mad_1
Regular Advisor

Re: Multi nodes cluster

Currently, several 2 nodes clusters are formed in my environment. A sample configuration is listed below:

Cluster I
=========
Node 1 with package A (running critical and heavy application)
Node 2 with package B (running less-critical and light application
Shared HASS as cluster lock disk.
Shared Model 10 disk array as data disk.
Lan and serial heartbeat configured.

Cluster II
==========
Node 3 with package C (running critical and heavy application)
Node 4 with package D (running less-critical and light application
lock disk & heartbeat are the same as Cluster I.

Cluster III & IV are similar to the above.

As you can see in all clusters, there is a less-critical and light package running. Therefore, I would like to combine several critical packages to form a 3 or 4 nodes cluster. Then less servers are required after cluster re-structure.

As I mentioned previously, my concern is on the cluster lock disk and heartbeat configuration.

Thank
Christopher McCray_1
Honored Contributor

Re: Multi nodes cluster

Hello,

John and anyone else may correct me on this, but I am certain that your current config isn't expandable in the area of your array hardware.

The Model 10 is only capable of connecting to up to two hosts, so there goes your lock disk. However, the lock disk is NOT REQUIRED, but RECOMMENDED, so you can look into the quorum server, or omit the lock disk altogether.

If your data array is the same then you will not be able to expand this as well because the shared disks MUST be visible to all nodes in your cluster. (If you can't hook up the arrays directly to all nodes, then your out).

The serial heartbeat is only supported with 2 node configurations, so you would have to go to a network heartbeat configuration, as a dedicated hb is only supported w/ 2nodes as well.

I apologize for not asking sooner what your config was as this is probably the most important aspect to a cluster and will limit you accordingly. Your issue is upgrading your disk components and the $$$$ involved (HA is expensive, isn't it??).

Good luck and have a merry Christmas.

Chris


It wasn't me!!!!
Mad_1
Regular Advisor

Re: Multi nodes cluster

Merry Christmas to all.

Chris

As I mentioned the new cluster configuration, the first 3 nodes run 3 primary packages respectively, the 4th node is the standby node for the first 3 nodes. Is it possible only the 4th node should view all shared disks, but not the first 3 nodes. As below:

|------| |------| |------|
| Node | | Node | | Node |
| A | | B | | C |
|------| |------| |------|
| | |
| | |
====== ====== ======
|disk| |disk| |disk|
| A | | B | | C |
====== ====== ======
| | |
| | |
| |------| |
|______| Node |_____|
| D |
|------|

That means Node A, B and C are not required to view all shared disk. Any node of A, B or C failed will trigger a package failover to node D. Then the Model 10 disk array could be re-used. Does MC/SG support this type of configuration.

Furthermore, is there any type of SCSI disk support to attach to multi nodes.

I studied the "Managing MC/SG", I found configure cluster is not an easy task. Only study the guide is not enough and many thing in the guide is not defined clearly.

Finally, I would like to say thanks to all of you for your help.











Mad_1
Regular Advisor

Re: Multi nodes cluster

Sorry the figure in my previous reply is distorted.

The figure is attached here.
Christopher McCray_1
Honored Contributor

Re: Multi nodes cluster

Hello,

I see now ( I think ) what you are talking about after referencing the guide and where it seems possible.

The problem is that I have never done this before. When I went to the training, all that was ever discussed in respect to the shared disks was that they need to be visible to all nodes, although certain pages in chapter 2 suggest otherwise.

It seems possible, however, I don't have the resources (and I suspect you don't either) to test this. I apologize for not being any more help, but I also don't want to give you fatal advise.

I'll look around, but for now, good luck.

Chris
It wasn't me!!!!
avsrini
Trusted Contributor

Re: Multi nodes cluster

Hi Mad,
You figure is very clear. And this setup is very well possible.

1. First configure the cluster with all 4 nodes without lock VG. You can use
Quorum server if you have one. I installed the quorum server and it is really very easy to setup it.
You have to just edit a file
in /etc/cmcluster/qs_authfile and add the nodes's name or IP address to use this as quorum server.

2. Configure VG's on Node A,B,C and vgimport on Node D.

3. Configure Packages to fallback to Node D.

4. If possible use multiple heartbeat links to the cluster.

If you need further help keep posting.

Happy clustering.

Srini
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Mad_1
Regular Advisor

Re: Multi nodes cluster

Thank you all! I've just finished my Christmas vacation. How did you spend your time in Christmas? Wish you all have a wonderful and fruitful new year.

After several rounds of questions and answer, I have a clearly view of multi nodes cluster.

I would like to ask 2 more questions:

1. Should the quarum server be the one of the cluster node? Or it must not be any one of the cluster node.

2. As I understand, cluster can only be started when 50% or more cluster nodes are alive and can communicate. Take a 3 nodes cluster as example, if one of the cluster node failed, then the other 2 nodes will take control and form a 2 nodes cluster. The question is ---- After this 2 nodes cluster formed successfully, if there is one more node failed (assume lock disk is configured), will there be single node cluster taking control (50% of 2 nodes cluster)? Or the whole cluster will fail and cannot be restarted (only one node survive, this is only 33.33% of the original 3 nodes cluster)?

Thanks


John Poff
Honored Contributor

Re: Multi nodes cluster

Hi Mad,

We had a great Christmas!

1. From what I remember reading about the quorum server, it has to be on a system that is not one of the nodes in the cluster, which kind of makes sense. The quorum server needs to be able to break the tie during an election if the cluster is reforming, and it wouldn't work if it was running on a node that failed.

2. When the cluster starts it expects to have communications with all the nodes, and the cluster won't start until the communication is successful to all nodes. You can force the cluster up on just one node. I have done that before when we were working on systems and I wanted to get things started. I think the 'cmruncl -f nodename' will start the cluster on a node without having all the other nodes up.

JP
Mad_1
Regular Advisor

Re: Multi nodes cluster

Most of my concern is the cluster lock disk.

Does anyone has experience configured lock disk in multi nodes cluster.

1. Which types of disk can be configured as cluster lock disk within multi nodes cluster?

2. How can the lock disk be configured / connected within the cluster, which make all nodes can view the lock disk?

Thanks
avsrini
Trusted Contributor

Re: Multi nodes cluster

Hi Mad,

1. Quorum server has to be a separate server other than cluster nodes. If you have even any workstations running
you can use it as quorum server.

2. Regarding Lock disk.
If you have a HA Disk Array, We have XP256, which is connected to all
the nodes, you can configure one single LUN on all the nodes and use it as lock disk.
If you dont have HA box, then try JBOD, a cheaper option. But i feel, you can
connect only 2 nodes to a JBOD.
If anybody knows how to connect 3 nodes to JBOD, pls help us.

When you run the cmquerycl command, when you initially
configure the cluster, this
will give you which disk you
can use as Lock disk.

3. ON 3 nodes cluster, if 2 nodes are down, i think the cluster will halt. You can't run with only one node.

Happy clustering.

Srini.
Be on top.