[Lustre-discuss] OST redundancy between nodes?

Carlos Santana neubyr at gmail.com
Thu Jun 25 08:21:07 PDT 2009


On Fri, Jun 19, 2009 at 1:15 PM, Kevin Van Maren<Kevin.Vanmaren at sun.com> 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 am confused about this. Will the files in that OST be unavailable or
some of the files in that filesystem be unavailable?
My impression is that lustre would stripe file data across many OSTs
in terms of objects. So wouldn't failure of one OST will potentially
corrupt the files which have stripes/objects stored over that OST?

Please correct me if I am wrong.

-
CS.

>>
>> 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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