[Lustre-discuss] Question about failnode

Kazuki Ohara ohara at rd.scei.sony.co.jp
Mon Oct 29 23:14:00 PDT 2007


Hi, Brain

Thank you for your answering many times.

Brian J. Murrell wrote:
> On Mon, 2007-10-29 at 16:58 +0900, Kazuki Ohara wrote:
>> I can't find out the reason why MGS and OSS need to learn of the failover partner.
> 
> Because the MGS is the centre (i.e. configuration broker if you will) of
> how a cluster is configured.  All nodes go to the MGS to get the cluster
> configuration.
> 
> Strictly speaking a given OST does not need to know who it's failover
> partner is, and the --failnode in the mkfs.lustre on the OST is not in
> to inform the OST (it's running on) but that information is sent (i.e.
> by mkfs.lustre) to the MGS so that the rest of the cluster (who do need
> to know) can learn this.

Nevertheless the OSSes itself don't need to know the failover partner,
who does need to get and use the information of the partner that is hold by the MGS?

> 
>> By that information, does MGS or OSS request the partner not to access the shared volume
>> or something special requests?
> 
> No.  You must keep in mind that exclusive access to the shared media is
> absolutely required.  I think you understand this, but it does bear
> repeating.
> 
> You must never have both OSSes mount the same volume at the same time --
> you will corrupt it.  Lustre itself does not take care of this mounting
> and unmounting however.  This is left to the operating environment that
> Lustre is running in -- Linux and can be achieved in Linux using
> Heartbeat.  Please see the manual for more information on how Heartbeat
> achieves this.

I'm sorry for making you worry.
I understood Lustre do nothing for exclusive accesses and it must be ensured by
Heartbeat and STONISH mechanism by your previous answer. But I wanted to write
something as an example of special requests and wrote such one.
I am not good at English, so I hope the things I want to express is expressed well.

Best regards,
Kazuki Ohara




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