[Lustre-devel] WBC HLD outline

Alexander Zarochentsev Alexander.Zarochentsev at Sun.COM
Wed Mar 25 09:17:29 PDT 2009

On 25 March 2009 11:33:12 Alex Zhuravlev wrote:
> >>>>> Alexander Zarochentsev (AZ) writes:
>  AZ> On 24 March 2009 02:17:33 Robert Read wrote:
>  >> Hi Zam,
>  >>
>  >> > MD update: a part of MD operation to be executed on one server,
>  >> > contains one or more MDS/RAW operations.
>  >>
>  >> Why does the client need to to be more granular than an update? 
>  >> It seems MDS/Raw and update should be the same.
>  AZ> well, better to say an update is MDS op if the operation touch
> only one AZ> MD server and MDS/Raw op in case of distributed
> operation.
> I think this just adds unneeded entity to the system. stating that
> we either have updates or operations is simpler.
>  >> Isn't this essentially what the cmm is doing today? (Breaking
>  >> down distributed operations into per-node updates?)  Are you
>  >> expanding on Alex's idea of creating a new generic MD server
>  >> stack?
>  AZ> I just doubt that cmm code reuse is worth MD stack relayering.
> Can it be AZ> done as a subtask later?
> I don't think CMM is right thing because it essentially breaks
> layering: instead of sending object creation request in terms of OSD
> API or index insert in terms of OSD API it introduces some
> intermediate thing which is neither operation nor update.

Server MD stack has to support both WBC and non-WBC clients for the same 
objects. It is why I think MDT layer should handle MD ops as well as 
MDS/RAW ops. Then CMM only passes RAW operations to MDD layer, where 
raw ops are already supported.

Alexander "Zam" Zarochentsev
Staff Engineer
Lustre Group, Sun Microsystems

More information about the lustre-devel mailing list