[rhelv6-list] Question about fence device network?

[Digimer]

On 08/19/2011 12:55 AM, solarflow99 wrote:
> i'm going through the guide too and I just wonder why you would even
> need fencing if you are not using something like GFS?  Imagine a network
> with many app servers running on their own storage, they would probably
> just link to a database to read/write any data. 

The cluster communication and membership layer is separate from the
resource management layer. The membership layer is concerned with having
nodes in a known state. So, when a node "disappears" (network failure,
hard failure, kernel panic, hung/blocked), the node falls into an
unknown state. The cluster blocks at will remain blocked until the lost
node is put into a known state. This is done using fencing.

By allowing the cluster to reliably reach out and force-off a node, the
node then is in a known state and recovery can begin. All of this
happens well below the resource manager, and is not dependant on whether
something like GFS2 is in use or not.

-- 
Digimer
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