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P4300 G2 and FOM High Availability

Andrea Asioli
Occasional Contributor

P4300 G2 and FOM High Availability

Hello,
I realized for a customer the infrastructure you see in the attached PDF.
A P4300 G2 SAS has been splitted in two different locations separated from 100 meters of OM4 fiber optics and the FailOver Manager has been installed in a third node visible from both the P4300 controllers.
At this point everything is working fine but the customer is worried about the chance that "Nodo B" and "Nodo C" disappears together (not remote chanche, they had a flooding few weeks ago that could reach this result)in this case even the machine on "Nodo A" will stop working due to missing FOM. My question is: is there any way to have two FOM in HA,or maybe Active/Stand-By, to have always at least one node always active and everything working in automatic way?
Or in case of this disaster I have to start manually a new FOM instance to have the system working again?
I forgot to mention that the two HP-DL380G7 are equipped with VMware vSphere 4.2 Advanced Edition.
Thank you in advance for your help.
4 REPLIES
Mark...
Honored Contributor

Re: P4300 G2 and FOM High Availability

Hi,
As far as I know it is NOT possible to have 2 x FOM or 1 and a standby etc in a management group.
You have *EITHER* a FOM *OR* a VM and *ONLY* 1 is allowed.
In your situation if you or your customer is worried about losing a node and the FOM at the same time then maybe you would be better off using the VM ??
Downside of the VM is that you have to manually start it but at least if you lose 1 node (in your case) you can always start the VM on the surviving node.
It's an option but you will have to decide what you think is best.
Mark...
if you have nothing useful to say, say nothing...
Andrea Asioli
Occasional Contributor

Re: P4300 G2 and FOM High Availability

Hello,

I need to understand better your answer: the FOM I mentioned is already a virtual machine running on VMware player in a dedicated small server, so I have a FOM in a third node, apart from the two vmware host.
On the two ESXi server I copied, in the internal HDs, a copy of the same FOM virtual machine I have on Node C. If I understand correctly your meaning I can have as many virtual machine I desire,with FOM inside, wherever I want but only one can be active. In case of disaster I need to start manually another FOM machine to take control of the remining P4300? Is it correct?
Mark...
Honored Contributor

Re: P4300 G2 and FOM High Availability

Hi,
Not really...
VM in this case means Virtual Manager.
With the P4000 you need to maintain Quorum (Q) otherwise access will be stopped to any volumes. In the P4000 this is achieved by the nodes that are running the manager process and each manager process has 1 vote. This can not be altered.
In your configuration you have two nodes which equals two votes (assuming both nodes are running the manager process)
Therefore your Q value = 2 and if one node "fails" for whatever reason you will lose Q and that means no access to your volumes till the problem is fixed.
The idea of the FOM or Virtual Manager (VM) is to act as a tie breaker.
So if you have two managers + FOM that equals 3 votes and Q of 2. Lose any one node OR the FOM and the cluster stays up. The thing about using the FOM is that it is automatic.If you do the same thing with the VM (that is use the VM instead of the FOM)then what you have to do is to create the VM (option in CMC) but DO NOT start the process. Should one of the nodes VM. Now if one of the nodes fails you will lose access to all the volumes but now you can start the VM process on the surviving node and Q will be restored and so you will have access to your volumes.
The key difference between FOM and VM is that FOM maintains Q automatically but using the VM you need to start the VM process to regain Q in the event of losing Q in the first place.
Hopefully that will help ??
Mark...
if you have nothing useful to say, say nothing...
Andrea Asioli
Occasional Contributor

Re: P4300 G2 and FOM High Availability

Thank you Mark. Now the thing it's clear. Thank you very much. Bye.