Minimum support lan setup for serviguard 11.16

[Richard I Curtis]

Hi,
I have an 11.16 cluster with the on-board lan, and two, dual port lan cards.
At present, I have:
lan0 -> lan0 via a crossover as a dedicated heartbeat network
lan1 -> switch -> lan1
lan3 -> switch -> lan3 (all four interfaces have link level connectivity)
and lan 2 and 4 on each host is used for something specific which I have no control over and have to remain dedicated to that purpose.

I have an requirement to release lan3 on each node to dedicate to some other specific kit which I have no control over.

Is it still a supported configuration for me to keep the cross over cable for dedicated heart beat, and have only one lan interface (without a failover interface) to carry the public connection? I realise that would leave me exposed to a single point of failure at each public lan connection, but as I have no available slots, short of swapping a dual port card for a quad port, will I still be supported ?

I have looked for any HP docs specifying the minimum supported requirements but all the examples I have seen show my current setup (ie, 1 dedicated lan for heartbeat, and 2 interfaces per node for public address failover)

I seem to recall cmcheckconf and cmapplyconf complaining if there is no failover interface.. have I dreamt that or if it does complain, can that be skipped somehow?

[melvyn burnard · Accepted solution]

Well as you say, if you remove a standby interface from your data LAN, you render yourself liable to issues caused by a SPOF.
However, provided you set that LAN as a heartbeat lan as well as teh crossover cable lan, then this would be supported.
Would you not be better served by removing teh crossover cable (which can have it's own issues) and rather put it through a switch and have that LAN as the standby for your data/Heartbeat LAN?

[Richard I Curtis]

>Well as you say, if you remove a standby interface from your data LAN, you render yourself liable to issues caused by a SPOF.

I am 100% behind that, but I may be in the position that I am not able to gain additional lan cards in the servers, and may have no choice but to give up this port at the cost of accepting we are less protected.

>However, provided you set that LAN as a heartbeat lan as well as teh crossover cable lan, then this would be supported.

Excellent - thanks for the confirmation.

>Would you not be better served by removing teh crossover cable (which can have it's own issues) and rather put it through a switch and have that LAN as the standby for your data/Heartbeat LAN?

Is that an option? I was under the (probably wrong) impression that you needed 2 heartbeat lans..
If I had it like:
lan0 - switch - lan0
lan1 - switch - lan1 (all four having link level connectivity)
with lan1 the main interface and lan0 as the standby interface for lan1, even if they were heartbeat interfaces, lan0 would be down without an IP, so I would be down to only one heartbeat lan. Would that work or am I missing something in my understanding of the config here?

[John Bigg]

It is an option, but I suggest you stick with what you suggested. If you combine lan0 and lan1 together that subnet itself becomes a single point of failure and even though the lan is no longer a SPOF if the subnet has problems, HB will not get through and you will have a node failure instead.

It's up to you to balance the risks. Both options are supported.

Personally, I'd get a quad port card and do it properly. Isn't this going to be cheaper than the risk to your business of having a SPOF for the data lan or the subnet?