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how to handle switch over when the cable is unplugged from hub

 
ITSD-ACCS
Frequent Advisor

how to handle switch over when the cable is unplugged from hub

Hello I have the following configuration in my cluster info :
HEARTBEAT_INTERVAL 500000
.....
NODE_NAME CEDLBS01
NETWORK_INTERFACE lan2
HEARTBEAT_IP 123.12.102.1
NETWORK_INTERFACE lan0
HEARTBEAT_IP 123.12.100.1
NETWORK_INTERFACE lan1
HEARTBEAT_IP 123.12.101.1
.....
.....
I got a notice from my network guy saying that he is going replace the hub by a switch. Each node (one from each server) has a cable connected to this hub. What will happen to the cluster ? Let's assume that it will last a few seconds.

Thanks a lot.
7 REPLIES 7
melvyn burnard
Honored Contributor

Re: how to handle switch over when the cable is unplugged from hub

well are ALL the heartbeats connected to the same hub? if yes, then you should halt the cluster.
If no, then there should be no problem, unless you have a network that you application is available on AND it's backup lan on the same hub.

One thing to bear in mind, is that you should look to fix the switch port and lan card's speed and duplexing mode, as if these try to auto negotiate, there have been some problems in various scenarios.

HTH
My house is the bank's, my money the wife's, But my opinions belong to me, not HP!
Dietmar Konermann
Honored Contributor

Re: how to handle switch over when the cable is unplugged from hub

If all HB networks rely on that central hub you will get a cluster reformation... depending on your NODE_TIMEOUT the cluster will reform if the connectivity comes back again fast enough. Otherwise... BANG. This is the cluster/heartbeat part of the problem.

The other aspect is about your package configuration... if packages depend on subnets (SUBNET statement in configuration) then they will be halted immediately if a subnet goes down. Detection depends on NETWORK_POLLING_INTERVAL.

Summary:
If the hub is a single point of failure, then it is NOT a good idea to try anything with it online.

Regards...
Dietmar.
"Logic is the beginning of wisdom; not the end." -- Spock (Star Trek VI: The Undiscovered Country)
ITSD-ACCS
Frequent Advisor

Re: how to handle switch over when the cable is unplugged from hub

Dear Melvyn & Dietmar,

Thank you for your response. Actually only 2 heartbeats IP are connected to hub, lan0 and lan1 indicated above. Please find below the timing and subnet configuration.

HEARTBEAT_INTERVAL 500000
NODE_TIMEOUT 2000000
AUTO_START_TIMEOUT 600000000
NETWORK_POLLING_INTERVAL 2000000

# My package parameter
IP[0]=123.12.100.3
SUBNET[0]=123.12.100.0
IP[1]=123.12.101.3
SUBNET[1]=123.12.101.0

Does that mean, if my network guys can do the replacement faster than 20 secs, there would be no problem ?

PS. I guess I have to do it offline then.
Dietmar Konermann
Honored Contributor

Re: how to handle switch over when the cable is unplugged from hub

Hi!

You make sure that at least one HB net keeps running then the cluster will be happy with that.

But you habe to look at your package configuraton. Are there SUBNET statements? You posted only the contents of your package control scripts. You need to look at the conf files instead.

Or do a:
cmviewconf |grep "package subnet"

If one if the listed subnets fails then the correspondig package will be halted after failure detection. The NETWORK_POLLING_INTERVAL determines how long the failure detection take at maximum. Of course SG may detect the failure even immediately if you unplug just before the next polling interval starts.


Regards...
Dietmar.
"Logic is the beginning of wisdom; not the end." -- Spock (Star Trek VI: The Undiscovered Country)
melvyn burnard
Honored Contributor

Re: how to handle switch over when the cable is unplugged from hub

Well this seems to show that your package will be on th elans that get moved, so I believe your package may try to shutdown and move, especially if the standby lans are also in the same hub.

I would suggest they move one cable at a time and then comnfirm the connection is good and that the systems can communicate over each lan.
You would also need to check your users can get to the relevant ip address on the lan that gets moved.
Otherwise, I suggest you think of halting the cluster if you are really concerned.
My house is the bank's, my money the wife's, But my opinions belong to me, not HP!
Sanjay_6
Honored Contributor

Re: how to handle switch over when the cable is unplugged from hub

Hi,

If you have standby lan configured the lan port being disconneted with switch to the standby lan. however, there is always a possibility of the crash. I would suggest a graceful shutdown before you start switching cables.

Hope this helps.

Regds
Oleg Zieaev_1
Regular Advisor

Re: how to handle switch over when the cable is unplugged from hub

I would recommend not to put both heartbeats to the same hub.
reconfigure one of the heartbeats to use your regular card for network traffic.
In such a case if your connection lost on the dedicated network, it will go to regular network to provide heartbeat.
We have this running in production. Just make sure your regular network is going to different switch.
Professionals will prevail ...