[Linux-cluster] Fence device, How it work

[Michael Will]

Lon Hohberger wrote:

>On Mon, 2005-11-07 at 11:37 +0000, nattapon viroonsri wrote:
>  
>
>>I tend to use APC AP7900 as fence device.
>>
>>So when failover have occure  backup node control  APC to power cycle 
>>failnode.
>>But im not sure how kind of  this device work .
>>Is it  just power off or power cycle at outlet that fail node was pluged ?
>>    
>>
>
>Power-cycle.
>  
>
I always wondered about this. If the node has a problem, chances are 
that rebooting does not
fix it. Now if the node comes up semi-functional and attempts to regain 
control over the ressource
that it owned before, then that could be bad. Should it not rather be 
shut-down so an human intervention
can fix it before it is being made operational again?

I/O fencing instead of power fencing kind of works like this, you undo 
the i/o block once you know
the node is fine again.

Michael

-- 
Michael Will
Penguin Computing Corp.
Sales Engineer
415-954-2822
415-954-2899 fx
mwill at penguincomputing.com