[Lustre-discuss] OST redundancy between nodes?

[Dr. Hung-Sheng Tsao (LaoTsao)]

it seems that one can use dual connected array to two nodes and use 
software mirroring between the two  array to give U double protection
1)HW-raid within array
2)SW raid between arrays
hth

Kevin Van Maren wrote:
> Gary Gogick wrote:
>   
>> Heya all,
>>
>> I'm investigating potential solutions for a storage deployment.  
>> Lustre piqued my interest due to ease of scalability and awesome 
>> aggregate throughput potential. 
>>
>> Wondering if there's any provision in Lustre for handling catastrophic 
>> loss of a node containing an OST; eg. replication/mirroring of OSTs to 
>> other nodes?
>>
>> I'm gathering from the 1.8.0 documentation that there's no protection 
>> of this sort for data other than underlying RAID configs on any 
>> individual node, at least not without attempting to do some 
>> interesting stuff with DRDB.  Just started looking at Lustre over the 
>> past day though, so I'd totally appreciate an authoritative answer in 
>> case I'm misinterpreting the documentation. :)
>>     
>
> Correct.
>
> Lustre failover can be used to support catastrophic failure of a _node_, 
> but not the _storage_.  If your configuration makes LUNs available to 
> two nodes, it is possible to configure Lustre to operate across the 
> failure of a server.
>
> If your LUN fails catastrophically, all the data on that lun is gone.  
> It is possible to bring Lustre up without it, but none of the files on 
> that OST would be available.  If you are concerned about this case, then 
> backups are your friend.
>
> While drdb could be used to make a lun "available" to two nodes, it will 
> have a significant impact on performance, and (AFAIK) does not do 
> synchronous replication, so an fsck would be required prior to mounting 
> the OST on the second node, and there would be some data loss.
>
> Kevin
>
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