Re: Director Failover

First off, piranha is nothing more than a name given to the "Frontend" 
or gui.  With that said, it utilizes the same ipvs tables as any other 
lvs Linux based solution.  If the other list says it can be done, my 
guess is they are doing a lot more hard-core hand coding to handle 
arping issues that the Piranha interface can not accomplish unless 
they've done some major work on. My guess is they haven't sense Advance 
Server is the new "flag ship". Of course I have no idea of the context 
of which you speak of so bare with me as I try to go into a little more 
detail for you.

The real key in making any lvs solution work is understanding how arp 
works.  What happens to arp tables on the director and boxes providing 
services when fail over occures can be monitored to help diagnose.  A 
sniffer, standard arp commands,  netcat and a few other tools that 
escape my brain are good diagnostic tools.  The key to seeing what the 
interfaces are seeing.  In the Cisco world all of the arp issues are 
taken care of at the router/director level and boxes behind it are saved 
from the arp issues and storms that can happen.  At one point the kernel 
team wasn't  putting patches into the kernel to handle lvs, I'm not sure 
if it is back in or removed forever??\

<Mike any time you want to jump in here feel free>

There are ways of setting up a combination of  lo interfaces along with 
iptables to handle some of these issues.  It is very cluge though and 
hard to maintain in my opinion.  I say lo interfaces because even dummy 
interfaces arp out.  :/  I'm not sure where they are with integrating 
back into the mainstream kernel patches that handle some of this (Mike 
?). You may also want to look at doing that.   I do know that Red Hat's 
Advanced Server handles a lot of these issues in a more comprehensible 
package.  It also uses shared SCSI in a better manner than Piranha can. 
 On the flip side there are a whole new set of issue with that solution 
that I don't want to get into.

Bottom line here is it is almost impossible for me to diagnose your 
setup via email.  What I can almost bet my life on is your most likely 
running into an arping issue that the plain "out of the box piranha" 
doesn't handle without minipulating the underlying parts that it sets on 
top off.

Hope this sheads some light, good luck.

Regards,
BMan



ong cheechye wrote:

>Hi BMan,
>
>I've read about questions raised on connection
>synchronization between the primary and backup
>director in the lvs mailing list. I suppose that means
>existing connection can be maintained during director
>failover. Does that means connection synchronization
>is achieved in other software but not Piranha ?
>
>During my test with piranha, I noticed the telnet
>session is still on shortly after the director
>failover but went dead eventually. How do you explain
>this observation ?
>
>Thanks
>Chee Chye
>
> --- BMan <[email protected]> wrote: > The
>existing telnet connection will be disconnected
>  
>
>>because Piranha 
>>(regardless of routing method used)  does not track
>>session state.  The 
>>same holds true for ssh, ftp and similar services.
>>
>>Regards,
>>BMan
>>
>>ong cheechye wrote:
>>
>>    
>>
>>>Hi,
>>>
>>>I'm testing Piranha+Direct routing with telnet
>>>      
>>>
>>service
>>    
>>
>>>using a primary director and a backup director
>>>      
>>>
>>which
>>    
>>
>>>is also acting as a realserver (due to shortage of
>>>machines). 
>>>
>>>I telnet from another machine to the VIP. I then
>>>      
>>>
>>stop
>>    
>>
>>>the pulse in the primary director and the backup
>>>director take over. Would the existing telnet
>>>connection be disconnected ?
>>>
>>>Thanks
>>>Chee Chye
>>> 
>>>
>>>__________________________________________________
>>>Do You Yahoo!?
>>>Promote your business from just $5 a month!
>>>http://sg.biztools.yahoo.com
>>>
>>>
>>>
>>>_______________________________________________
>>>Piranha-list mailing list
>>>[email protected]
>>>      
>>>
>>https://listman.redhat.com/mailman/listinfo/piranha-list
>>    
>>
>>> 
>>>
>>>      
>>>
>>
>>
>>_______________________________________________
>>Piranha-list mailing list
>>[email protected]
>>
>>    
>>
>https://listman.redhat.com/mailman/listinfo/piranha-list 
>
>__________________________________________________
>Do You Yahoo!?
>Promote your business from just $5 a month!
>http://sg.biztools.yahoo.com
>
>
>
>_______________________________________________
>Piranha-list mailing list
>[email protected]
>https://listman.redhat.com/mailman/listinfo/piranha-list
>
>  
>