[Linux-cluster] Fencing agents

[Denis Medvedev]

Adam Manthei пишет:

>On Wed, Aug 03, 2005 at 11:58:47AM +0000, "Sævaldur Arnar Gunnarsson [Hugsmiðjan]" wrote:
>  
>
>>I'm implementing a shared storage between multiple (2 at the moment) 
>>Blade machines (Dell PowerEdge 1855) running RHEL4 ES connected to a EMC 
>>AX100 through FC.
>>
>>The SAN has two FC ports so the need for a FC Switch has not yet come 
>>however we will add other Blades in the coming months.
>>The one thing I haven't got figured out with GFS and the Cluster-Suite 
>>is the whole idea about fencing.
>>    
>>
>
>Funny timing :)  I just checked in the fencing agent for the PowerEdge
>1855's a couple days ago!  
>
>(http://sources.redhat.com/cgi-bin/cvsweb.cgi/cluster/fence/agents/drac/fence_drac.pl?rev=1.3.4.2&content-type=text/x-cvsweb-markup&cvsroot=cluster)
>
>  
>
>>The fencing agents in that setup is manual fencing.
>>    
>>
>
>I would strongly discourage this.
>
>  
>
>>What does "automatic" fencing have to offer that the manual fencing lacks.
>>If we decide to buy the FC switch right away is it recomended that we 
>>buy one of the ones that have fencing agent available for the 
>>Cluster-Suite ?
>>    
>>
>
>In this case, you already have a fencing agent (fence_drac) that works with
>the PE 1855 blades so there is no need for further fencing hardware (unless
>you are going to be connecting other machines to the cluster that aren't
>going to have any other form of fencing)
>
>The main advantage that "automatic" fencing gives you over manual fencing is
>that in the event that a fencing operation is required, your cluster can
>automatically recover (on the order of seconds to minutes) instead of waiting
>for user intervention (which can take minutes to hours to days depending on
>how attentive the admins are :).    
>
>  
>
"recover"? You mean reboot? But if a machine need fencing, doesn't that 
mean that something is inherently wrong with that machine and simple 
reboot would't cure that?