You are absolutely correct on that statement.  Migration (for performance 
reasons) does NOT reconstruct aggregated bitfiles.  Thus expired (or 
reclaimable space) in the aggregate is not 'reclaimed' at the point of 
migration.  One of the chief reasons for this, other than performance, was the 
thought that data migrating typically from disk is being done so quickly after 
the files were inserted into storage that the return on investment would be 
very low.  That is, we would not find much space to reclaim given the effort 
put out to search for it.

Keith Davey
TSM Level 2 Support
kjdavey AT us.ibm DOT com


zark wrote:
> At 10:26 AM 4/26/2009, Nick Laflamme wrote:
>
> > On Apr 26, 2009, at 9:03 AM, Remco Post wrote:
> >
> >
> > > On Apr 26, 2009, at 12:10 , Peter Buschman wrote:
> > >
> > >
> > > > Apologies if this is a well-known question but I am scratching my
> > > > head trying to answer it.
> > > >
> > > > Basically, what I want to know is if a migration job in TSM job will
> > > > also migrate expired data on the volumes it is migrating.  In a
> > > > sense, I am wondering if part of the effect of reclamation can be
> > > > achieved through initiating migration to another storage pool.
> > > >
> > > > If data is migrated from one storage pool to another, do the volumes
> > > > in the new storage pool still contain expired files that were in the
> > > > first storage pool after the migration?
> > > >
> > >
> > > Expired data is not in the TSM database any more, so it can't be
> > > migrated.
> > >
> >
> > Without contradicting Remco's point, I'll add that the MOVE DATA
> > command includes an optional parameter, RECONSTRUCT, that would
> > influence the recovery of space used by files expired from an
> > aggregate of data. This option may occasionally trigger some confusion
> > about when space used by expired files is recovered during copy
> > procedures.
> >
>
> If I am not mistaken, migration does not reconstruct aggregates, but rather
> moves them in their entirety.  Thus, expired data contained within an
> aggregate with other active data will be migrated to tape.  I believe the
> only processes that re-aggregate data are RECLAIM and MOVE DATA (when the
> RECONSTRUCT=YES option is specified).
>
> Files that are not aggregated with others (i.e., standalone) would not get
> migrated, of course.
>
> ..Paul
>
>
>
> --
> Paul Zarnowski                            Ph: 607-255-4757
> Manager, Storage Services                 Fx: 607-255-8521
> 719 Rhodes Hall, Ithaca, NY 14853-3801    Em: psz1 < at > cornell.edu


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