[CentOS] Cluster Heart Beat Using Cross Over Cable

John R Pierce pierce at hogranch.com
Thu Nov 6 16:49:21 UTC 2008


Morten Torstensen wrote:
> lingu wrote:
>>  Since it is a very critical and busy server may be due to heavy
>> network load  some hear beat signal is getting missed  resulting in
>> shifting of service from one node to another.
>
> For automated takeover systems, especially critical ones (tho you can 
> argue that any system setup with automatic takeover is critical by 
> definition), you should have multiple heartbeat paths. Ethernet, 
> serial cable, on shared disk, fibre or whatnot.
>
> Having false takeovers due to missed heartbeat on one set of ethernet 
> cards could also likely be missed on another set of cards, even with a 
> crossover cable.
>
> Maybe you should investigate alternate paths?
>

indeed, commercial cluster software like Veritas REQUIRES dual path 
dedicated heartbeat networks, and highly recommends implementing storage 
'fencing' so that there's no way physically possible both systems could 
simultaneously mount the storage.

fencing is fairly easy with SAN storage, you instruct the SAN switch to 
only allow the currently active server to have access to the storage, 
and when the standby server takes over, it instructs the switch to 
disable access by the old active server before enabling access by 
itself.   fencing with shared scsi is much harder and requires special 
hardware.


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