Hi Dave...

It depends. (doesn't everything?)

Actually, collocation just means that ADSM tries to keep all the data for a
client together, it does NOT necessarily mean each client gets a private
tape.

If the MAXSCRATCH parameter for you tape storage pool keeps the available
tapes less than the number of clients you have, then ADSM has no choice but
to put multiple clients on a tape.

If you have a mainframe class tape robot and beaucoup 2-GB cartridges, there
is no reason not to give ADSM lots of tapes to play with, and then
collocation will generally result in each client being separate on its own
tapes.

But here, as an example, we are backing up 400 desktops, averaging about 2
GB each, into a robot that contains only 262 cartridges.  We don't have
space in the robot for one cartridge per client, and don't need it because
the tapes hold 70 GB each and the clients are small.  So I have MAXSCRATCH
set to 100 in my tape pool, and ADSM puts multiple clients on each
cartridge.  (I use the other cartridges for my archive pool, copy pool,
etc.)

We still get the desired benefit of collocation - which is to have the
client's data together so as to minimized tape mounts required for restores.
ADSM will put the data from Client A's Tuesday backup on the same tape that
he put Client A's Monday backup, and put Client B's Tuesday backup on the
same tape that he put Client B's Monday backup, etc, so collocation is
maintained for every client.  Even if there are several clients on the same
tape, when  you do a restore, skipping over somebody else's data on the same
tape takes seconds; doing 100 tape mounts to restore the client would take a
lot longer.

Hope this clarifies it some.

Wanda



.

> -----Original Message-----
> From: Sanders, David [SMTP:DSanders AT INTERNAL.MASSMUTUAL DOT COM]
> Sent: Thursday, January 14, 1999 11:42 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: colocation and reclaimation for a local storagepool
>
> Wanda (and others);
> you said as one part of the response:
> "If the input cartridge has several clients' data on it:
> ADSM will repeat the process above for EACH client on the input tape."
>
> I thought that this wouldn't happen with collocation?  Or would that
> condition be a result of reclaimation on collocated volumes?
>
> Dave Sanders
> Sr. Technical Consultant
> MassMutual / The Blue Chip Company
> 1295 State St, E060, Springfield, MA 01111
> 413-744-5095