[Linux-cluster] Fence device, How it work

[Lon Hohberger]

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.

> If so failnode was shutdown  or reboot uncleanly ? (look like no ups when 
> have no power)

It is an "unclean" power-off.

> Im afraid of data corrupt may occur.

Most journalled file systems will just replay the journal and life will
continue after it reboots.

> Or cluster manager instruct failnode to shutdown before instruct APC to 
> power cycle ? ( So it reboot or shutdown cleanly)

It does not instruct the node to shut down.  It turns off the power to
the node.  When a node appears down, it is currently assumed that we can
no longer communicate with it, so telling it to shut down will not work.

(This isn't always the case, but for now, this is how it works.)

-- Lon