> > I agree that it is likely that the SRM databases and file catalogs
> > will get out of sync, but this is the system that we have to work with
> > at the moment. I think sites (where their resources allow) are already
> > trying to minimise the effect of failures by having some form of
> > resiliency built in (database backups, RAID, file replicas, redundant
> > power supplies...).
> >
> > Greig
>
When I said SRM databases I meant the namespace database on an SRM storage
element. File catalogs referred to the Grid file catalogs. Apologies for
any confusion.
I agree that a good solution of grid catalogs and storage element file
systems getting out of sync would be for the SRMs to report on the files
that are available within them (maybe using some sort of srmLs, as has
been mentioned on this thread before) and higher level middleware dealing
with any inconsistencies found.
Greig
>
> Sorry to correct you here Greg but the SRM database holds SRM requests,
> hence Derek has dropped this database multiple time in the past for Tier
> 1 and not the file system name space as may be implied by your choice of
> words. Like any project of any size developers MUST make considerable
> effort to avoid having duplicate state (or code) unless this is well
> managed and designed in at day one (Eg Message Queues and Touple
> spaces).
>
>
> D-cache uses PNFS for file system name space management (Through an
> POSIX file/directory API) this is effectively a view of the PNFS
> databases, in the same way as the Castor SRM uses a conventional RDBMS
> (Oracle) view to see the name server within Castor. Both the Castor and
> D-Cache databases for SRM do not contain duplicate file system
> catalogues.
>
> The Replica catalogue and the SRM do have duplication for grid files but
> SRM's must also support local usage. These will and do get out of sync,
> It is my opinion the the replica management services should resolve
> these inconsistencies issues and SRM's should report on availability of
> files within them.
>
> Regards
>
> Owen
>
> >
> > --
> > =====================================================================
> > === Dr Greig A Cowan
> > http://www.ph.ed.ac.uk/~gcowan1
> > School of Physics, University of Edinburgh, James Clerk Maxwell
> > Building
> >
> > TIER-2 STORAGE SUPPORT PAGES:
> > http://wiki.gridpp.ac.uk/wiki/Grid_Storage
> > =====================================================================
> > ===
>
>
>
--
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Dr Greig A Cowan http://www.ph.ed.ac.uk/~gcowan1
School of Physics, University of Edinburgh, James Clerk Maxwell Building
TIER-2 STORAGE SUPPORT PAGES: http://wiki.gridpp.ac.uk/wiki/Grid_Storage
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