Sorry to be replying so late on this thread, I am just back from
a weeks absence.  Collocation clusters are filespaces for ordinary
clients.  For api clients like notes they may be filespaces also or something
that equates to a filespace in the database.

Reclaim not only squeezes out the empty space in aggregates, but it also
brings together all the pieces of each filespace, which means it has to
skip down the tape to get to each piece;  the server will know where to
skip to, it isn't reading all blocks and hunting.  For the initial post with 
4000+
clusters, that's a lot of skipping!  It will depend on how many times this
tape was the object of a migration task and thus how many pieces of each
filespace are on the tape.

In addition, if the target storage pool is collocated, each cluster may
ask for a new output tape, and tsm isn't smart enough to find all the
clusters that are bound for a particular output tape and reclaim them together.
Instead it is driven by the order of filespaces on the input tape, so the same
output tape may be mounted many times.

Move data does the same thing but without the aggregate squeeze.


--
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--------------------------
Bill Colwell
Bill Colwell
C. S. Draper Lab
Cambridge, Ma.
bcolwell AT draper DOT com
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In <200103051521.KAA67468 AT acs-mail.bu DOT edu>, on 03/05/01
In <200103051521.KAA67468 AT acs-mail.bu DOT edu>, on 03/05/01
   at 03:24 PM, Richard Sims <rbs AT BU DOT EDU> said:

>>Though we may have collocation activated in the server, I believe it to be
>> the general case that API-based clients either cannot or do not collocate.
>>(This is the case with HSM, at least.)  API-based clients which back up
>>numerous small client files thus pose a special burden on the server.

>To correct my own posting, this is what should have appeared:

> Though Aggregation occurs with the standard clients, I believe it to be
> the general case that API-based clients either cannot or do not Aggregate.
> (This is the case with HSM, at least.)  API-based clients which back up
> numerous small client files thus pose a special burden on the server.

>Sorry if I confused anyone.  My brain preoccupied with the blizzard that
>is going on outside.  And me without a sled!

>  Richard Sims, BU