[Lustre-discuss] MGS Nids

[Kevin Van Maren]

leen smit wrote:
> Ok, no VIP's then.. But how does failover work in lustre then?
> If I setup everything using the real IP and then mount from a client and 
> bring down the active MGS, the client will just sit there until it comes 
> back up again.
> As in, there is no failover to the second node.  So how does this 
> internal lustre failover mechanism work?
>
> I've been going trought the docs, and I must say there is very little on 
> the failover mechanism, apart from mentions that a seperate app should 
> care of that. Thats the reason I'm implementing keepalived..
>   
Right: the external service needs to keep the "mount" active/healthy on 
one of the servers.
Lustre handles reconnecting clients/servers as long as the volume is 
mounted where it expects
(ie, the mkfs node or the --failover node).
> At this stage I really am clueless, and can only think of creating a TUN 
> interface, which will have the VIP address (thus, it becomes a real IP, 
> not just a VIP).
> But I got a feeling that ain't the right approach either...
> Is there any docs available where a active/passive MGS setup is described?
> Is it sufficient to define a --failnode=nid,...  at creation time?
>   
Yep.  See Johann's email on the MGS, but for the MDTs and OSTs that's 
all you have to do
(besides listing both MGS NIDs at mkfs time).

For the clients, you specify both MGS NIDs at mount time, so it can 
mount regardless of which
node has the active MGS.

Kevin

> Any help would be greatly appreciated!
>
> Leen
>
>
> On 05/20/2010 01:45 PM, Brian J. Murrell wrote:
>   
>> On Thu, 2010-05-20 at 12:46 +0200, leen smit wrote:
>>    
>>     
>>> Keepalive uses a VIP in a active/passive state. In a failover situation
>>> the VIP gets transferred to the passive one.
>>>      
>>>       
>> Don't use virtual IPs with Lustre.  Lustre clients know how to deal with
>> failover nodes that have different IP addresses and using a virtual,
>> floating IP address will just confuse it.
>>
>> b.
>>
>>    
>>     
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