At the end, this will be an aesthetic call, but:

On 11/30/2011 03:10 PM, Hans Christian Riksheim wrote:

Collocation is about paying, in unused tape space, for efficient
restores;  I'd suggest you view that as a bargain, not a burden.

Having our tapes extremely under utilized to achieve some kind of
acceptable performance is a burden. [...]
We don't have the time to do extensive micro management to reach a
compromise between unacceptable tape utilization and unacceptable
restore times.

You say "extremely" here, and "extensive".  I don't think that's been
suggested.

To be concrete: most of my volumes are full.  I run a script I wrote
to recommend new collocgroup assignments and removals, once a month
"Or so".  Koff.  I don't think I've run it in the last three months.

tsm: CTRL>erp,ext,ext2,int: select avg(pct_utilized) from volumes where
devclass_name='3592DEV' and status != 'PENDING'
                       Unnamed[1]
---------------------------------
  72.4010723860589812332439678284

                       Unnamed[1]
---------------------------------
  75.0089700996677740863787375415

                       Unnamed[1]
---------------------------------
  79.8164948453608247422680412371

                       Unnamed[1]
---------------------------------
  64.1396313364055299539170506912

That's not fantastically high utilization, but I don't think it's
"extremely underutilized", either.  And that's 1300+ nodes.


Time invested: maybe a half-hour per month ("or so"), plus a pleasant
afternoon or two writing the script (which you may have; it's in the
archives along with several other folks' solution to the same problem)

I'll actually run my script, act on its recommendations, and quote the
results again.

I only see using disk as a solution here. At least for incrementals.

really the trade-off here is between equipment and expertise.  It's
rational to choose the former, but the result will be that you're
doing things more expensively than is necessary.

- Allen S. Rout