"Role" addressing in other Linux installs [HA/Genesys]

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"Role" addressing in other Linux installs [HA/Genesys]

Post by jazzepat » 25 Jan 2012 20:31

Hi guys
Not sure if this is the correct place to post this, but Im curious on how I might be able to get this to work.
As far as Im concerned Alcatel-Lucent's use of having a virtual IP address for role addressing between 2 appliances works extremely well and is only dependant on the 2 servers themselves to decide which CPU should have the role / virtual address at any one time.
What Id like to know is if the same method ALU uses in Linux can be used in other Linux installs? In my case, I think this method could work brilliantly in Genesys installs of SIP Server and Resource Manager, 2 components that rely on a virtual IP address between 2 servers for HA purposes.
The documentation Genesys provide for this isn't quite right, and we've managed to do something that does work, but requires Nagios monitoring to work.. this got me thinking that it works really well on the OXE (in my 12 years of OXE experience Ive never had an issue where 2 CPU's have gone main at the same time) and was wondering if any of you gurus on here know how ALU have achieved this.
Ive done some preliminary digging around and found that the /etc/rc.d/init.d/netadmin process calls on /usr/netadm/data/netdata which contains the virtual IP information, so I think I could probably define the values, what Im not sure next is how does one CPU monitor the other CPU as to know who should have this address and then how does it decide when one CPU as the interface up or down?
I don't really know that much about scripting so Im not sure what else it might call in... Im also not sure what might be specific OXE stuff and what I solely need just to perform the function Im after..
Any help would be greatly appreciated

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Re: "Role" addressing in other Linux installs [HA/Genesys]

Post by krzysioD » 29 Jan 2012 18:49

Search for the "floating ip address technique" in teams on HA/redundancy.
It's very common thing. And it's not only appliances, it WAS used many, many years before the Linux was host OS - so it's rather OLD technology.
Ping is the master key, each CPU "pings" each other (in simple words, it's much more than simple ping-pong in means of ICMP).
To be more precise, the main gives instructions to the stand-by. (database updates on hdd, some parts of memory are even copied! like place where big table of who talks with who is stored - so called the half-coms :D )
And also it does "ping" so called in ALU world - reference rack (or Crystal one might say).
Also the "double main" or "pseudo main" in ALU world, in other places the "Split-brain" scenario is a good thing to learn (when N - in ALU only 2 CPUs think that they are the MAIN!).
If you put just two appliances running without ethernet - they will do strange things. Just watch them. Same with CPU7 :)
And yes, this is not OXE/ALU specific question. Search for some High Availability or Redundancy solutions in more unix-generic places - if you want for more info.
Please note that at no time I will provide you with OXE/4400 nor AOS releases.
Note that it's our private time, that we spent to help you, so please don't expect complete solution for your problem.
You will need to do homework by your self.

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