We've never had any severe problems, but we have seen I/O errors on our DLT
tapes.  But, AFAIK, no media is immune to those.
The reclamation process continually rolls viable data over to new media, so
that takes care of the "freshness".
The only issue we have had is that after several months or years of
incrementals the data gets spread over more and more volumes... resulting
in more and more mounts during a restore.  This even occurs on collocated
storage pools as older reclaimed data gets mixed with newly backed up data.
A periodic "absolute" backup would consolidate everything on minimum number
of volumes, but of course you need a larger backup window to accomodate it.

Robin Sharpe
Berlex Labs



                    Adam J Boyer
                    <adam.j.boyer
                    @FRB.GOV>     To:    ADSM-L AT VM.MARIST DOT EDU
                                  cc:    (bcc: Robin Sharpe/WA/USR/SHG)
                    12/17/01      Subject:
                    09:31 AM             Incremental forever -- any problems?
                    Please
                    respond to
                    "ADSM: Dist
                    Stor Manager"







Hey,

Our management is wondering if it's safe to just do incrementals
forever, or whether we should try to do a forced full every few months
to keep things fresh.  Our experience has been that the incremental
system works great-- we once restored a whole raid 5 array, with many
files from years ago.  But, nonetheless, I'd appreciate any stories or
testaments to help build a case.

Thanks much,
adam