HeartBeat IP

[Dhananjaya Amarakoon]

Hi Friends...

I have two Rx servers that are running SG. Both servers HB cables are connected through separate switch insted of cross cable(direct connect two servers).

What is the recommended way to use this ?
What is the advantage of using switch than use cross cable or other way round ?

Thnaks & Regards

Dhananjaya Amarakoon.

[Andrew Young_2]

Hi.

It is always recommended that heartbeat LAN runs through a switch. It makes it easier to work out if the heartbeat failure is an NIC, cable fault or network failure. Crossover cable configurations are no longer supported.

Regards

Andrew Y

[Ninad_1]

Few points I would highlight

If you use direct cross-over cables between the 2 servers, then
1. You reduce the flexibility to add more servers to the cluster later on - which would require you to reconnect to switch later on.
2. If you are going to have only 2 node cluster, then this reduces the points of failure (as switch would have introduced additional point of failure)
3. I dont think I have seen this as a recommended way, although this would work fine.

If you use switch
1. This gives you flexibility for future expansion
2. You would also need to connect the 2 switches to each other, because otherwise, in the event of a n/w port failure of one server would cause it to use the other other port connected to the other switch, whereas the 2nd server, which still continues to use its 1st port connected to 1st switch [ as there is no failure for that server ]. This was the point highlighted during our design by HP engg.

Regards,
Ninad

[Dhananjaya Amarakoon]

Hi Andrew
Thanks for your reply...

I too agree with your suggested points. But let me know is there any technical reason for not use cross cable for heartbeat communions? Why do you say "Crossover cable configurations are no longer supported".Is it because of above reason or latest SG not supporting cross cables.?

Thanks & Regards
Dhananjaya Amarakoon

[Andrew Young_2]

Hi.

Essentially the problem is this. In the case of a crossover cable if the cable fails then both servers will see the heartbeat connection has failed as has the heartbeat network. They will look at the link status to see if it was their side of the heartbeat link thats failed. Since they both think the problem may be with themselves they may both attempt to failover.

Added to this is that fact that crossover cables are notoriously unreliable, especially at Gigabit + speeds because they tend to be homemade and often too short.

However this is an unlikely situation since if the Service Guard cluster is correctly configured then the heartbeat should fail over to the public LAN first. However there is a timing delay with the switchover which reduces reliability.

There are probably other issues involved with this but this is what was explained to me, during our installation.

HTH

Andrew Y

[Shardha]

hi,

There is no problem in using the cross over cable, if you have an alternate link configured for the heart beat.
I have configured one clusters with one heart beat and standby network for this heartbeat, over aswitch. second heartbeat over a cross over cable. it is working fine.
Shardha

[John Bigg]

It is untrue to say that cross over cables are not supported. They are still supported and there are pro's and con's with them. But bottom line is that they are a fully supported configuration.