[Lustre-devel] GSS cross-realm on MDT -> OST

[Eric Mei]

Hi Ben,

Benjamin Bennett wrote:
> Hi Eric,
> 
>   If you could give me your input on something I'd greatly appreciate 
> it.  Or, if I should just sent this to -devel let me know...

Yes you can always send to -devel for open discussions. I'm CCing it.

>   For Lustre-WAN across TeraGrid we were hoping to distribute OSSs 
> across several resource providers (sites), leveraging existing kerberos 
> infrastructure, placing OSSs in each resource provider's local kerberos 
> realm, and the MDS in the teragrid realm.  Unfortunately, MDT -> OST 
> connections will not allow the MDT and OST to be in different realms, 
> since an OSS considers an MDS to be anyone holding a lustre_mds 
> principal in their local realm.
> 
>   This also seems undesirable within a single-realm where multiple 
> lustre clusters may exist, as an OSS in cluster A will trust an MDS for 
> cluster B, and an OSS for cluster B will trust an MDS for cluster A.
> 
>   My first thought was to add functionality to tell the OSSs lsvcgssd 
> what the trusted MDS principals should be (local or not).  Do you have 
> any thoughts on this?

We just never thought the usage that OSS could locate in multiple 
realms. I agree with you in this case, we can make OSS configurable to 
only accept designated lustre_mds principals, local or remote.

I'v questions just for curiosity: 1) is the benefit of cross site OSSs 
about bandwidth? 2) in the future with CMD (clustered metadata, multiple 
MDS nodes), would it be useful to distribute MDSs across multiple site 
as well?

Thanks
-- 
Eric