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.prat...@jasi.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 <bev...@fhcrc.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
