[ale] Linux HA

[James P. Kinney III]

On Wed, 2007-10-31 at 15:28 -0400, Charles Shapiro wrote:
> I believe that what you are looking for is what one ALE lecturer
> called a "STONITH Interface" ("Shoot the Other Node in the Head").  

And the poor man's STONITH interface - the X10 appliance module.
> 
> -- CHS
> 
> 
> On 10/31/07, Christopher Fowler <cfowler at outpostsentinel.com> wrote:
>         I've been testing some stuff in regards to Linux HA
>         today.  Normally we
>         sell 2 servers.  One is a "master" and the other is a
>         "slave".  I've
>         been testing today the capability to use a floating IP address
>         and allow 
>         the slave to take over for the master.  I have a few issues
>         that do need
>         to be resolved before I can roll this out.  In my lab and colo
>         I
>         experienced 2 issues that HA could not have saved me from.
>         
>         #1.  Kernel not responding. 
>         
>         In this case I can ping the server.  All connect()'s from
>         clients
>         seem to hang until they timeout.  In this scenario my slave
>         will take
>         the IP address but the master will still have it and still
>         answer pings. 
>         Also he will still answer arp requests.  HA can't save me
>         here.
>         
>         #2.  Kernel and programs still respond but disks are off
>         
>         In this case I/O to drives was hosed.  Apache would serve up
>         pages that
>         were in memory but any request in a page on disk would result
>         in that 
>         connection hanging forever.  No I/O possible.  In this
>         scenario the
>         heartbeat agent will probably still see a server that is
>         working but the
>         reality would be a DoS condition.  Also upon seeing this issue
>         I'm still 
>         left with a server who will not relinquish his IP address.
>         
>         In both cases it seems my only recourse is to allow my slave
>         to also
>         control the power of the master.  If #1 and #2 exist the slave
>         can
>         simply take the floating IP and make a determination if he
>         needs to kill 
>         power.  If so he can kill power and then the master can be
>         repaired.
>         
>         Ideas?
>         
>         Chris
>         
>         
>         
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>         http://www.ale.org/mailman/listinfo/ale
> 
> 
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-- 
James P. Kinney III          
CEO & Director of Engineering 
Local Net Solutions,LLC        
770-493-8244                    
http://www.localnetsolutions.com

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney at localnetsolutions.com>
Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7
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