Re: Objy/ROOT discussion at today's phone meeting

[Torre Wenaus <wenaus@bnl.gov>]

>   Can anyone allay my concerns?  Does anyone else share them?
I'm convinced! I share your concern

"David M. Malon" wrote:
> 
> >
> >  This is what I understood of the usage of ROOT for MDC2:
> >
> >  * Storage Manager will not be affected.
> >  * ROOT will contain some event components.
> >  * SM will provide Objy OID's and FID's and it's up to codes to find out
> >  what files to look for the events in. I.e., the codes will do the FID to
> >  ROOT file name mapping.
> >  * Objy's catalog for mapping of FID to filename will be used for ROOT
> >  files too.
> >
> >  Comments?
> >  _________________________________________
> >  Henrik Nordberg       <hnordberg@lbl.gov>
> >  Scientific Data Management Research Group
> >  Lawrence Berkeley National Laboratory
> >
> 
>    This is my understanding as well, with the clarification that the SM
>    will ALSO be a client of the FID-to-filename mapping, so that the
>    Cache Manager can deliver the correct files by the time the user code
>    tries to reach them.
> 
>    I am not yet comfortable with the proposed approach to generating
>    FIDs for ROOT files, but Henrik's text does correctly describe the
>    current proposal.  I have no objection to having Objectivity manage
>    the FID-to-name mapping; it's the consumption of Objectivity DB ids
>    (there are only 64K of them available--scalability implications?) and
>    faking Objectivity into believing that ROOT files are federation databases
>    (implications for database administration operations (install,
>    attach/detach, copy, ...?) that still bother me.  (Some Objectivity tools
>    check whether an alleged database file is really an Objectivity database.)
>    There are certainly other ways to generate unique FIDs between ROOT and
>    Objectivity, as well as other ways to let Objectivity manage the mapping.
> 
>    I realize that the proposed approach will probably be okay for MDC2.
>    Scalability, though, is the GCA's raison d'etre, so I am reluctant to
>    deceive Objectivity in a way that may diminish scalability unless there
>    is a good reason for it.
> 
>    Can anyone allay my concerns?  Does anyone else share them?
> 
>    Cheers,
> 
>    David

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