Hi Bill,

I like Wanda's point. MAXSCRatch is the best way to control tape usage. You
can probably write a fun select to see how many nodes have data on the
average tape. In Wanda's example, there are about 2 nodes per tape. If you
see that that number gets too high, you can increase MAXSCRatch.

On Thu, Jan 15, 2009 at 11:53 AM, Wanda Prather <wanda.prather AT jasi DOT 
com>wrote:

> Collocation consumes as much of the library as you tell it to.
>
> When you set MAXSCRATCH on a storage pool, TSM will confine the pool to
> that
> number of tapes.  If you have less tapes available than you have clients,
> you get a "do the best you can" collocation.
>
> There are plenty of sites who have more clients than slots in their
> library.
>
> If you have 100 clients and set MAXSCRATCH for the pool to 50 tapes, TSM
> will put each client on a different tape until it hits 50, then it will
> double up.
>
> You still get a decent amount of collocation; it's a lot faster for a
> restore to skip over another clients data on the same tape, than it is to
> rewind, dismount, mount, and reposition to a different tape.
>
> What you have to remember if you are collocating, is that you have to check
> your pools periodically and reevaluate maxscratch for the pool.  If your
> total amount of data is growing, you will need to up the maxscratch
> periodically so that you maintain enough available free tapes in the pool
> to
> provide a reasonable level of collocation.
>
> W
>
> On Thu, Jan 15, 2009 at 1:34 PM, Evans, Bill <bevans AT fhcrc DOT org> wrote:
>
> > Is there a guide or rule of thumb for determining what collocation will
> > do to library space?  It is being considered for improving restore
> > speeds.
> >
> > I'm backing up 80TB in 30 volumes(filespaces) on a solaris server.
> > Currently there is no collocation set, all data goes to a long-term
> > management class, single onsite and off-site tape pools, data churn
> > averages < 1TB/night.
> >
> > Using a 650 slot L700 library, LTO3, TSM 5.5, AIX 5.3.  The library is
> > >80% full, so, I'm concerned that starting collocation for the volumes
> > will consume the rest of the library.  Each filespace collocation may
> > end up with one tape not full (or 30 in this case).
> > Thanks,
> > Bill Evans
> > Research Computing Support
> > FRED HUTCHINSON CANCER RESEARCH CENTER
> >
>



--
Sam Rawlins